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This chapter describes Emacs features for maintaining large programs. The version control features (see section Version Control) are also particularly useful for this purpose.
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A change log file contains a chronological record of when and why you have changed a program, consisting of a sequence of entries describing individual changes. Normally it is kept in a file called `ChangeLog' in the same directory as the file you are editing, or one of its parent directories. A single `ChangeLog' file can record changes for all the files in its directory and all its subdirectories.
The Emacs command C-x 4 a adds a new entry to the change log
file for the file you are editing
(add-change-log-entry-other-window). If that file is actually
a backup file, it makes an entry appropriate for the file's
parent--that is useful for making log entries for functions that
have been deleted in the current version.
C-x 4 a visits the change log file and creates a new entry unless the most recent entry is for today's date and your name. It also creates a new item for the current file. For many languages, it can even guess the name of the function or other object that was changed.
When the variable add-log-keep-changes-together is
non-nil, C-x 4 a adds to any existing item for the file
rather than starting a new item.
If add-log-always-start-new-record is non-nil,
C-x 4 a always makes a new entry, even if the last entry
was made by you and on the same date.
If the value of the variable change-log-version-info-enabled
is non-nil, C-x 4 a adds the file's version number to the
change log entry. It finds the version number by searching the first
ten percent of the file, using regular expressions from the variable
change-log-version-number-regexp-list.
The change log file is visited in Change Log mode. In this major mode, each bunch of grouped items counts as one paragraph, and each entry is considered a page. This facilitates editing the entries. C-j and auto-fill indent each new line like the previous line; this is convenient for entering the contents of an entry.
You can use the command M-x change-log-merge to merge other log files into a buffer in Change Log Mode, preserving the date ordering of entries.
Version control systems are another way to keep track of changes in your program and keep a change log. See section Features of the Log Entry Buffer.
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A change log entry starts with a header line that contains the current
date, your name, and your email address (taken from the variable
add-log-mailing-address). Aside from these header lines, every
line in the change log starts with a space or a tab. The bulk of the
entry consists of items, each of which starts with a line starting
with whitespace and a star. Here are two entries, both dated in May
1993, with two items and one item respectively.
1993-05-25 Richard Stallman <rms@gnu.org>
* man.el: Rename symbols `man-*' to `Man-*'.
(manual-entry): Make prompt string clearer.
* simple.el (blink-matching-paren-distance):
Change default to 12,000.
1993-05-24 Richard Stallman <rms@gnu.org>
* vc.el (minor-mode-map-alist): Don't use it if it's void.
(vc-cancel-version): Doc fix.
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One entry can describe several changes; each change should have its own item, or its own line in an item. Normally there should be a blank line between items. When items are related (parts of the same change, in different places), group them by leaving no blank line between them.
You should put a copyright notice and permission notice at the end of the change log file. Here is an example:
Copyright 1997, 1998 Free Software Foundation, Inc. Copying and distribution of this file, with or without modification, are permitted provided the copyright notice and this notice are preserved. |
Of course, you should substitute the proper years and copyright holder.
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A tags table is a description of how a multi-file program is broken up into files. It lists the names of the component files and the names and positions of the functions (or other named subunits) in each file. Grouping the related files makes it possible to search or replace through all the files with one command. Recording the function names and positions makes possible the M-. command which finds the definition of a function by looking up which of the files it is in.
Tags tables are stored in files called tags table files. The conventional name for a tags table file is `TAGS'.
Each entry in the tags table records the name of one tag, the name of the
file that the tag is defined in (implicitly), and the position in that
file of the tag's definition. When a file parsed by etags is
generated from a different source file, like a C file generated from a
Cweb source file, the tags of the parsed file reference the source
file.
Just what names from the described files are recorded in the tags table depends on the programming language of the described file. They normally include all file names, functions and subroutines, and may also include global variables, data types, and anything else convenient. Each name recorded is called a tag.
See also the Ebrowse facility, which is tailored for C++. See (ebrowse)Top section `Ebrowse' in Ebrowse User's Manual.
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Here is how tag syntax is defined for the most popular languages:
In C code, any C function or typedef is a tag, and so are definitions of
struct, union and enum.
#define macro definitions, #undef and enum
constants are also
tags, unless you specify `--no-defines' when making the tags table.
Similarly, global variables are tags, unless you specify
`--no-globals', and so are struct members, unless you specify
`--no-members'. Use of `--no-globals', `--no-defines'
and `--no-members' can make the tags table file much smaller.
You can tag function declarations and external variables in addition
to function definitions by giving the `--declarations' option to
etags.
In C++ code, in addition to all the tag constructs of C code, member
functions are also recognized; member variables are also recognized,
unless you use the `--no-members' option. Tags for variables and
functions in classes are named `class::variable' and
`class::function'. operator definitions have
tag names like `operator+'.
In Java code, tags include all the constructs recognized in C++, plus
the interface, extends and implements constructs.
Tags for variables and functions in classes are named
`class.variable' and `class.function'.
In LaTeX text, the argument of any of the commands \chapter,
\section, \subsection, \subsubsection,
\eqno, \label, \ref, \cite,
\bibitem, \part, \appendix, \entry,
\index, \def, \newcommand, \renewcommand,
\newenvironment or \renewenvironment is a tag.
Other commands can make tags as well, if you specify them in the
environment variable TEXTAGS before invoking etags. The
value of this environment variable should be a colon-separated list of
command names. For example,
TEXTAGS="mycommand:myothercommand" export TEXTAGS |
specifies (using Bourne shell syntax) that the commands `\mycommand' and `\myothercommand' also define tags.
In Lisp code, any function defined with defun, any variable
defined with defvar or defconst, and in general the first
argument of any expression that starts with `(def' in column zero is
a tag.
In Scheme code, tags include anything defined with def or with a
construct whose name starts with `def'. They also include variables
set with set! at top level in the file.
Several other languages are also supported:
In Ada code, functions, procedures, packages, tasks and types are tags. Use the `--packages-only' option to create tags for packages only.
In Ada, the same name can be used for different kinds of entity (e.g., for a procedure and for a function). Also, for things like packages, procedures and functions, there is the spec (i.e. the interface) and the body (i.e. the implementation). To make it easier to pick the definition you want, Ada tag name have suffixes indicating the type of entity:
package body.
function.
task.
procedure.
package spec.
type.
Thus, M-x find-tag RET bidule/b RET will go
directly to the body of the package bidule, while M-x
find-tag RET bidule RET will just search for any tag
bidule.
In assembler code, labels appearing at the beginning of a line, followed by a colon, are tags.
In Bison or Yacc input files, each rule defines as a tag the nonterminal it constructs. The portions of the file that contain C code are parsed as C code.
In Cobol code, tags are paragraph names; that is, any word starting in column 8 and followed by a period.
In Erlang code, the tags are the functions, records and macros defined in the file.
In Fortran code, functions, subroutines and block data are tags.
In HTML input files, the tags are the title and the h1,
h2, h3 headers. Also, tags are name= in anchors
and all occurrences of id=.
In Lua input files, all functions are tags.
In makefiles, targets are tags; additionally, variables are tags unless you specify `--no-globals'.
In Objective C code, tags include Objective C definitions for classes, class categories, methods and protocols. Tags for variables and functions in classes are named `class::variable' and `class::function'.
In Pascal code, the tags are the functions and procedures defined in the file.
In Perl code, the tags are the packages, subroutines and variables
defined by the package, sub, my and local
keywords. Use `--globals' if you want to tag global variables.
Tags for subroutines are named `package::sub'. The
name for subroutines defined in the default package is
`main::sub'.
In PHP code, tags are functions, classes and defines. Vars are tags too, unless you use the `--no-members' option.
In PostScript code, the tags are the functions.
In Prolog code, tags are predicates and rules at the beginning of line.
In Python code, def or class at the beginning of a line
generate a tag.
You can also generate tags based on regexp matching (see section Etags Regexps) to handle other formats and languages.
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The etags program is used to create a tags table file. It knows
the syntax of several languages, as described in
Source File Tag Syntax.
Here is how to run etags:
etags inputfiles… |
The etags program reads the specified files, and writes a tags
table named `TAGS' in the current working directory.
If the specified files don't exist, etags looks for
compressed versions of them and uncompresses them to read them. Under
MS-DOS, etags also looks for file names like `mycode.cgz'
if it is given `mycode.c' on the command line and `mycode.c'
does not exist.
etags recognizes the language used in an input file based on
its file name and contents. You can specify the language with the
`--language=name' option, described below.
If the tags table data become outdated due to changes in the files described in the table, the way to update the tags table is the same way it was made in the first place. If the tags table fails to record a tag, or records it for the wrong file, then Emacs cannot possibly find its definition until you update the tags table. However, if the position recorded in the tags table becomes a little bit wrong (due to other editing), the worst consequence is a slight delay in finding the tag. Even if the stored position is very far wrong, Emacs will still find the tag, after searching most of the file for it. That delay is hardly noticeable with today's computers.
Thus, there is no need to update the tags table after each edit. You should update a tags table when you define new tags that you want to have listed, or when you move tag definitions from one file to another, or when changes become substantial.
One tags table can virtually include another. Specify the included tags file name with the `--include=file' option when creating the file that is to include it. The latter file then acts as if it covered all the source files specified in the included file, as well as the files it directly contains.
If you specify the source files with relative file names when you run
etags, the tags file will contain file names relative to the
directory where the tags file was initially written. This way, you can
move an entire directory tree containing both the tags file and the
source files, and the tags file will still refer correctly to the source
files. If the tags file is in `/dev', however, the file names are
made relative to the current working directory. This is useful, for
example, when writing the tags to `/dev/stdout'.
When using a a relative file name, it should not be a symbolic link pointing to a tags file in a different directory, because this would generally render the file names invalid.
If you specify absolute file names as arguments to etags, then
the tags file will contain absolute file names. This way, the tags file
will still refer to the same files even if you move it, as long as the
source files remain in the same place. Absolute file names start with
`/', or with `device:/' on MS-DOS and MS-Windows.
When you want to make a tags table from a great number of files, you
may have problems listing them on the command line, because some systems
have a limit on its length. The simplest way to circumvent this limit
is to tell etags to read the file names from its standard input,
by typing a dash in place of the file names, like this:
find . -name "*.[chCH]" -print | etags - |
Use the option `--language=name' to specify the language
explicitly. You can intermix these options with file names; each one
applies to the file names that follow it. Specify
`--language=auto' to tell etags to resume guessing the
language from the file names and file contents. Specify
`--language=none' to turn off language-specific processing
entirely; then etags recognizes tags by regexp matching alone
(see section Etags Regexps).
The option `--parse-stdin=file' is mostly useful when
calling etags from programs. It can be used (only once) in
place of a file name on the command line. Etags will read from
standard input and mark the produced tags as belonging to the file
file.
`etags --help' outputs the list of the languages etags
knows, and the file name rules for guessing the language. It also prints
a list of all the available etags options, together with a short
explanation. If followed by one or more `--language=lang'
options, it outputs detailed information about how tags are generated for
lang.
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The `--regex' option provides a general way of recognizing tags based on regexp matching. You can freely intermix this option with file names, and each one applies to the source files that follow it. If you specify multiple `--regex' options, all of them are used in parallel. The syntax is:
--regex=[{language}]/tagregexp/[nameregexp/]modifiers
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The essential part of the option value is tagregexp, the regexp for matching tags. It is always used anchored, that is, it only matches at the beginning of a line. If you want to allow indented tags, use a regexp that matches initial whitespace; start it with `[ \t]*'.
In these regular expressions, `\' quotes the next character, and all the GCC character escape sequences are supported (`\a' for bell, `\b' for back space, `\d' for delete, `\e' for escape, `\f' for formfeed, `\n' for newline, `\r' for carriage return, `\t' for tab, and `\v' for vertical tab).
Ideally, tagregexp should not match more characters than are needed to recognize what you want to tag. If the syntax requires you to write tagregexp so it matches more characters beyond the tag itself, you should add a nameregexp, to pick out just the tag. This will enable Emacs to find tags more accurately and to do completion on tag names more reliably. You can find some examples below.
The modifiers are a sequence of zero or more characters that
modify the way etags does the matching. A regexp with no
modifiers is applied sequentially to each line of the input file, in a
case-sensitive way. The modifiers and their meanings are:
Ignore case when matching this regexp.
Match this regular expression against the whole file, so that multi-line matches are possible.
Match this regular expression against the whole file, and allow `.' in tagregexp to match newlines.
The `-R' option cancels all the regexps defined by preceding `--regex' options. It too applies to the file names following it. Here's an example:
etags --regex=/reg1/i voo.doo --regex=/reg2/m \
bar.ber -R --lang=lisp los.er
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Here etags chooses the parsing language for `voo.doo' and
`bar.ber' according to their contents. etags also uses
reg1 to recognize additional tags in `voo.doo', and both
reg1 and reg2 to recognize additional tags in
`bar.ber'. reg1 is checked against each line of
`voo.doo' and `bar.ber', in a case-insensitive way, while
reg2 is checked against the whole `bar.ber' file,
permitting multi-line matches, in a case-sensitive way. etags
uses only the Lisp tags rules, with no user-specified regexp matching,
to recognize tags in `los.er'.
You can restrict a `--regex' option to match only files of a
given language by using the optional prefix {language}.
(`etags --help' prints the list of languages recognized by
etags.) This is particularly useful when storing many
predefined regular expressions for etags in a file. The
following example tags the DEFVAR macros in the Emacs source
files, for the C language only:
--regex='{c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/'
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When you have complex regular expressions, you can store the list of
them in a file. The following option syntax instructs etags to
read two files of regular expressions. The regular expressions
contained in the second file are matched without regard to case.
--regex=@case-sensitive-file --ignore-case-regex=@ignore-case-file |
A regex file for etags contains one regular expression per
line. Empty lines, and lines beginning with space or tab are ignored.
When the first character in a line is `@', etags assumes
that the rest of the line is the name of another file of regular
expressions; thus, one such file can include another file. All the
other lines are taken to be regular expressions. If the first
non-whitespace text on the line is `--', that line is a comment.
For example, we can create a file called `emacs.tags' with the following contents:
-- This is for GNU Emacs C source files
{c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/\1/
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and then use it like this:
etags --regex=@emacs.tags *.[ch] */*.[ch] |
Here are some more examples. The regexps are quoted to protect them from shell interpretation.
Tag Octave files:
etags --language=none \
--regex='/[ \t]*function.*=[ \t]*\([^ \t]*\)[ \t]*(/\1/' \
--regex='/###key \(.*\)/\1/' \
--regex='/[ \t]*global[ \t].*/' \
*.m
|
Note that tags are not generated for scripts, so that you have to add a line by yourself of the form `###key scriptname' if you want to jump to it.
Tag Tcl files:
etags --language=none --regex='/proc[ \t]+\([^ \t]+\)/\1/' *.tcl |
Tag VHDL files:
etags --language=none \ --regex='/[ \t]*\(ARCHITECTURE\|CONFIGURATION\) +[^ ]* +OF/' \ --regex='/[ \t]*\(ATTRIBUTE\|ENTITY\|FUNCTION\|PACKAGE\ \( BODY\)?\|PROCEDURE\|PROCESS\|TYPE\)[ \t]+\([^ \t(]+\)/\3/' |
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Emacs has at any time one selected tags table, and all the commands for working with tags tables use the selected one. To select a tags table, type M-x visit-tags-table, which reads the tags table file name as an argument, with `TAGS' in the default directory as the default.
Emacs does not actually read in the tags table contents until you
try to use them; all visit-tags-table does is store the file
name in the variable tags-file-name, and setting the variable
yourself is just as good. The variable's initial value is nil;
that value tells all the commands for working with tags tables that
they must ask for a tags table file name to use.
Using visit-tags-table when a tags table is already loaded
gives you a choice: you can add the new tags table to the current list
of tags tables, or start a new list. The tags commands use all the tags
tables in the current list. If you start a new list, the new tags table
is used instead of others. If you add the new table to the
current list, it is used as well as the others.
You can specify a precise list of tags tables by setting the variable
tags-table-list to a list of strings, like this:
(setq tags-table-list
'("~/emacs" "/usr/local/lib/emacs/src"))
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This tells the tags commands to look at the `TAGS' files in your `~/emacs' directory and in the `/usr/local/lib/emacs/src' directory. The order depends on which file you are in and which tags table mentions that file, as explained above.
Do not set both tags-file-name and tags-table-list.
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The most important thing that a tags table enables you to do is to find the definition of a specific tag.
Find first definition of tag (find-tag).
Find next alternate definition of last tag specified.
Go back to previous tag found.
Find a tag whose name matches pattern (find-tag-regexp).
Find the next tag whose name matches the last pattern used.
Find first definition of tag, but display it in another window
(find-tag-other-window).
Find first definition of tag, and create a new frame to select the
buffer (find-tag-other-frame).
Pop back to where you previously invoked M-. and friends.
M-. (find-tag) is the command to find the definition of
a specified tag. It searches through the tags table for that tag, as a
string, and then uses the tags table info to determine the file that the
definition is in and the approximate character position in the file of
the definition. Then find-tag visits that file, moves point to
the approximate character position, and searches ever-increasing
distances away to find the tag definition.
If an empty argument is given (just type RET), the balanced expression in the buffer before or around point is used as the tag argument. See section Expressions with Balanced Parentheses.
You don't need to give M-. the full name of the tag; a part
will do. This is because M-. finds tags in the table which
contain tag as a substring. However, it prefers an exact match
to a substring match. To find other tags that match the same
substring, give find-tag a numeric argument, as in C-u
M-.; this does not read a tag name, but continues searching the tags
table's text for another tag containing the same substring last used.
If you have a real META key, M-0 M-. is an easier
alternative to C-u M-..
Like most commands that can switch buffers, find-tag has a
variant that displays the new buffer in another window, and one that
makes a new frame for it. The former is C-x 4 ., which invokes
the command find-tag-other-window. The latter is C-x 5 .,
which invokes find-tag-other-frame.
To move back to places you've found tags recently, use C-u - M-.; more generally, M-. with a negative numeric argument. This command can take you to another buffer. C-x 4 . with a negative argument finds the previous tag location in another window.
As well as going back to places you've found tags recently, you can go
back to places from where you found them. Use M-*, which
invokes the command pop-tag-mark, for this. Typically you would
find and study the definition of something with M-. and then
return to where you were with M-*.
Both C-u - M-. and M-* allow you to retrace your steps to
a depth determined by the variable find-tag-marker-ring-length.
The command C-M-. (find-tag-regexp) visits the tags that
match a specified regular expression. It is just like M-. except
that it does regexp matching instead of substring matching.
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The commands in this section visit and search all the files listed in the selected tags table, one by one. For these commands, the tags table serves only to specify a sequence of files to search. These commands scan the list of tags tables starting with the first tags table (if any) that describes the current file, proceed from there to the end of the list, and then scan from the beginning of the list until they have covered all the tables in the list.
Search for regexp through the files in the selected tags table.
Perform a query-replace-regexp on each file in the selected tags table.
Restart one of the commands above, from the current location of point
(tags-loop-continue).
M-x tags-search reads a regexp using the minibuffer, then
searches for matches in all the files in the selected tags table, one
file at a time. It displays the name of the file being searched so you
can follow its progress. As soon as it finds an occurrence,
tags-search returns.
Having found one match, you probably want to find all the rest. To find
one more match, type M-, (tags-loop-continue) to resume the
tags-search. This searches the rest of the current buffer, followed
by the remaining files of the tags table.
M-x tags-query-replace performs a single
query-replace-regexp through all the files in the tags table. It
reads a regexp to search for and a string to replace with, just like
ordinary M-x query-replace-regexp. It searches much like M-x
tags-search, but repeatedly, processing matches according to your
input. See section Replacement Commands, for more information on query replace.
You can control the case-sensitivity of tags search commands by
customizing the value of the variable tags-case-fold-search. The
default is to use the same setting as the value of
case-fold-search (see section Searching and Case).
It is possible to get through all the files in the tags table with a single invocation of M-x tags-query-replace. But often it is useful to exit temporarily, which you can do with any input event that has no special query replace meaning. You can resume the query replace subsequently by typing M-,; this command resumes the last tags search or replace command that you did.
The commands in this section carry out much broader searches than the
find-tag family. The find-tag commands search only for
definitions of tags that match your substring or regexp. The commands
tags-search and tags-query-replace find every occurrence
of the regexp, as ordinary search commands and replace commands do in
the current buffer.
These commands create buffers only temporarily for the files that they have to search (those which are not already visited in Emacs buffers). Buffers in which no match is found are quickly killed; the others continue to exist.
It may have struck you that tags-search is a lot like
grep. You can also run grep itself as an inferior of
Emacs and have Emacs show you the matching lines one by one.
See section Searching with Grep under Emacs.
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Display a list of the tags defined in the program file file.
Display a list of all tags matching regexp.
M-x list-tags reads the name of one of the files described by the selected tags table, and displays a list of all the tags defined in that file. The "file name" argument is really just a string to compare against the file names recorded in the tags table; it is read as a string rather than as a file name. Therefore, completion and defaulting are not available, and you must enter the file name the same way it appears in the tags table. Do not include a directory as part of the file name unless the file name recorded in the tags table includes a directory.
M-x tags-apropos is like apropos for tags
(see section Apropos). It finds all the tags in the selected tags table
whose entries match regexp, and displays them. If the variable
tags-apropos-verbose is non-nil, it displays the names
of the tags files together with the tag names.
You can customize the appearance of the output by setting the
variable tags-tag-face to a face. You can display additional
output with M-x tags-apropos by customizing the variable
tags-apropos-additional-actions--see its documentation for
details.
You can also use the collection of tag names to complete a symbol name in the buffer. See section Completion for Symbol Names.
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It's not unusual for programmers to get their signals crossed and modify the same program in two different directions. To recover from this confusion, you need to merge the two versions. Emerge makes this easier. For other ways to compare files, see Comparing Files, and Ediff: (ediff)Top section `Top' in The Ediff Manual.
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To start Emerge, run one of these four commands:
Merge two specified files.
Merge two specified files, with reference to a common ancestor.
Merge two buffers.
Merge two buffers with reference to a common ancestor in a third buffer.
The Emerge commands compare two files or buffers, and display the comparison in three buffers: one for each input text (the A buffer and the B buffer), and one (the merge buffer) where merging takes place. The merge buffer shows the full merged text, not just the differences. Wherever the two input texts differ, you can choose which one of them to include in the merge buffer.
The Emerge commands that take input from existing buffers use only the accessible portions of those buffers, if they are narrowed. See section Narrowing.
If a common ancestor version is available, from which the two texts to be merged were both derived, Emerge can use it to guess which alternative is right. Wherever one current version agrees with the ancestor, Emerge presumes that the other current version is a deliberate change which should be kept in the merged version. Use the `with-ancestor' commands if you want to specify a common ancestor text. These commands read three file or buffer names--variant A, variant B, and the common ancestor.
After the comparison is done and the buffers are prepared, the interactive merging starts. You control the merging by typing special merge commands in the merge buffer (see section Merge Commands). For each run of differences between the input texts, you can choose which one of them to keep, or edit them both together.
The merge buffer uses a special major mode, Emerge mode, with commands for making these choices. But you can also edit the buffer with ordinary Emacs commands.
At any given time, the attention of Emerge is focused on one particular difference, called the selected difference. This difference is marked off in the three buffers like this:
vvvvvvvvvvvvvvvvvvvv text that differs ^^^^^^^^^^^^^^^^^^^^ |
Emerge numbers all the differences sequentially and the mode line always shows the number of the selected difference.
Normally, the merge buffer starts out with the A version of the text. But when the A version of a difference agrees with the common ancestor, then the B version is initially preferred for that difference.
Emerge leaves the merged text in the merge buffer when you exit. At
that point, you can save it in a file with C-x C-w. If you give a
numeric argument to emerge-files or
emerge-files-with-ancestor, it reads the name of the output file
using the minibuffer. (This is the last file name those commands read.)
Then exiting from Emerge saves the merged text in the output file.
Normally, Emerge commands save the output buffer in its file when you exit. If you abort Emerge with C-], the Emerge command does not save the output buffer, but you can save it yourself if you wish.
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You can choose between two modes for giving merge commands: Fast mode and Edit mode. In Fast mode, basic merge commands are single characters, but ordinary Emacs commands are disabled. This is convenient if you use only merge commands. In Edit mode, all merge commands start with the prefix key C-c C-c, and the normal Emacs commands are also available. This allows editing the merge buffer, but slows down Emerge operations.
Use e to switch to Edit mode, and C-c C-c f to switch to Fast mode. The mode line indicates Edit and Fast modes with `E' and `F'.
Emerge has two additional submodes that affect how particular merge commands work: Auto Advance mode and Skip Prefers mode.
If Auto Advance mode is in effect, the a and b commands advance to the next difference. This lets you go through the merge faster as long as you simply choose one of the alternatives from the input. The mode line indicates Auto Advance mode with `A'.
If Skip Prefers mode is in effect, the n and p commands skip over differences in states prefer-A and prefer-B (see section State of a Difference). Thus you see only differences for which neither version is presumed "correct." The mode line indicates Skip Prefers mode with `S'.
Use the command s a (emerge-auto-advance-mode) to set or
clear Auto Advance mode. Use s s
(emerge-skip-prefers-mode) to set or clear Skip Prefers mode.
These commands turn on the mode with a positive argument, turns it off
with a negative or zero argument, and toggle the mode with no argument.
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In the merge buffer, a difference is marked with lines of `v' and `^' characters. Each difference has one of these seven states:
The difference is showing the A version. The a command always produces this state; the mode line indicates it with `A'.
The difference is showing the B version. The b command always produces this state; the mode line indicates it with `B'.
The difference is showing the A or the B state by default, because you haven't made a choice. All differences start in the default-A state (and thus the merge buffer is a copy of the A buffer), except those for which one alternative is "preferred" (see below).
When you select a difference, its state changes from default-A or default-B to plain A or B. Thus, the selected difference never has state default-A or default-B, and these states are never displayed in the mode line.
The command d a chooses default-A as the default state, and d b chooses default-B. This chosen default applies to all differences which you haven't ever selected and for which no alternative is preferred. If you are moving through the merge sequentially, the differences you haven't selected are those following the selected one. Thus, while moving sequentially, you can effectively make the A version the default for some sections of the merge buffer and the B version the default for others by using d a and d b between sections.
The difference is showing the A or B state because it is preferred. This means that you haven't made an explicit choice, but one alternative seems likely to be right because the other alternative agrees with the common ancestor. Thus, where the A buffer agrees with the common ancestor, the B version is preferred, because chances are it is the one that was actually changed.
These two states are displayed in the mode line as `A*' and `B*'.
The difference is showing a combination of the A and B states, as a result of the x c or x C commands.
Once a difference is in this state, the a and b commands don't do anything to it unless you give them a numeric argument.
The mode line displays this state as `comb'.
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Here are the Merge commands for Fast mode; in Edit mode, precede them with C-c C-c:
Select the previous difference.
Select the next difference.
Choose the A version of this difference.
Choose the B version of this difference.
Select difference number n.
Select the difference containing point. You can use this command in the merge buffer or in the A or B buffer.
Quit--finish the merge.
Abort--exit merging and do not save the output.
Go into Fast mode. (In Edit mode, this is actually C-c C-c f.)
Go into Edit mode.
Recenter (like C-l) all three windows.
Specify part of a prefix numeric argument.
Also specify part of a prefix numeric argument.
Choose the A version as the default from here down in the merge buffer.
Choose the B version as the default from here down in the merge buffer.
Copy the A version of this difference into the kill ring.
Copy the B version of this difference into the kill ring.
Insert the A version of this difference at point.
Insert the B version of this difference at point.
Put point and mark around the difference.
Scroll all three windows down (like M-v).
Scroll all three windows up (like C-v).
Scroll all three windows left (like C-x <).
Scroll all three windows right (like C-x >).
Reset horizontal scroll on all three windows.
Shrink the merge window to one line. (Use C-u l to restore it to full size.)
Combine the two versions of this difference (see section Combining the Two Versions).
Show the names of the files/buffers Emerge is operating on, in a Help window. (Use C-u l to restore windows.)
Join this difference with the following one. (C-u x j joins this difference with the previous one.)
Split this difference into two differences. Before you use this command, position point in each of the three buffers at the place where you want to split the difference.
Trim identical lines off the top and bottom of the difference. Such lines occur when the A and B versions are identical but differ from the ancestor version.
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The q command (emerge-quit) finishes the merge, storing
the results into the output file if you specified one. It restores the
A and B buffers to their proper contents, or kills them if they were
created by Emerge and you haven't changed them. It also disables the
Emerge commands in the merge buffer, since executing them later could
damage the contents of the various buffers.
C-] aborts the merge. This means exiting without writing the output file. If you didn't specify an output file, then there is no real difference between aborting and finishing the merge.
If the Emerge command was called from another Lisp program, then its
return value is t for successful completion, or nil if you
abort.
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Sometimes you want to keep both alternatives for a particular difference. To do this, use x c, which edits the merge buffer like this:
#ifdef NEW version from A buffer #else /* not NEW */ version from B buffer #endif /* not NEW */ |
While this example shows C preprocessor conditionals delimiting the two
alternative versions, you can specify the strings to use by setting
the variable emerge-combine-versions-template to a string of your
choice. In the string, `%a' says where to put version A, and
`%b' says where to put version B. The default setting, which
produces the results shown above, looks like this:
"#ifdef NEW\n%a#else /* not NEW */\n%b#endif /* not NEW */\n" |
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During the merge, you mustn't try to edit the A and B buffers yourself. Emerge modifies them temporarily, but ultimately puts them back the way they were.
You can have any number of merges going at once--just don't use any one buffer as input to more than one merge at once, since the temporary changes made in these buffers would get in each other's way.
Starting Emerge can take a long time because it needs to compare the
files fully. Emacs can't do anything else until diff finishes.
Perhaps in the future someone will change Emerge to do the comparison in
the background when the input files are large--then you could keep on
doing other things with Emacs until Emerge is ready to accept
commands.
After setting up the merge, Emerge runs the hook
emerge-startup-hook.
See section Hooks.
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This document was generated by Mark Kaminski on July, 3 2008 using texi2html 1.70.