0. 理解 git diff 返回信息
1. 命令
$ git diff README.md
2. 返回信息，注解
diff --git a/README.md b/README.md ## 1. 表示为你使用的git格式的diff：
index d29ab50..7e42b29 100644 ## 2. 表示两个版本的git哈希值，（index区域的d29ab50对象，
## 与工作目录区域的7e42b29对象进行比较）
## 最后的六位数字是对象的模式（普通文件，644权限）
--- a/README.md ## 3.1 "---"表示变动前的版本，
+++ b/README.md ## 3.2 "+++"表示变动后的版本。
@@ -37,3 +37,4 @@ ## 4. 表示变动的位置，用两个@作为起首和结束：
##4.1 前面的"-37,3"分成三个部分：减号表示第一个文件（即index区域的d29ab50对象），"37"表示第37行，"3"表示连续3行。
## 合在一起，就表示下面是第一个文件从第37行开始的连续3行。
##
##4.2 "+37,4"表示变动后，成为第二个文件从第37行开始的连续4行。
You can get it using command `hostname` in your remote robot:
$ hostname
+Enjoy it!
3. git diff --help
NAME
git-diff - Show changes between commits, commit and working tree, etc
SYNOPSIS
git diff [options] [<commit>] [--] [<path>...]
git diff [options] --cached [<commit>] [--] [<path>...]
git diff [options] <commit> <commit> [--] [<path>...]
git diff [options] <blob> <blob>
git diff [options] [--no-index] [--] <path> <path>
DESCRIPTION
Show changes between the working tree and the index or a tree, changes between the
index and a tree, changes between two trees, changes between two blob objects, or
changes between two files on disk.
git diff [--options] [--] [<path>...]
This form is to view the changes you made relative to the index (staging area
for the next commit). In other words, the differences are what you could tell
Git to further add to the index but you still haven't. You can stage these
changes by using git-add(1).
git diff --no-index [--options] [--] [<path>...]
This form is to compare the given two paths on the filesystem. You can omit the
--no-index option when running the command in a working tree controlled by Git
and at least one of the paths points outside the working tree, or when running
the command outside a working tree controlled by Git.
git diff [--options] --cached [<commit>] [--] [<path>...]
This form is to view the changes you staged for the next commit relative to the
named <commit>. Typically you would want comparison with the latest commit, so
if you do not give <commit>, it defaults to HEAD. If HEAD does not exist (e.g.
unborn branches) and <commit> is not given, it shows all staged changes.
--staged is a synonym of --cached.
git diff [--options] <commit> [--] [<path>...]
This form is to view the changes you have in your working tree relative to the
named <commit>. You can use HEAD to compare it with the latest commit, or a
branch name to compare with the tip of a different branch.
git diff [--options] <commit> <commit> [--] [<path>...]
This is to view the changes between two arbitrary <commit>.
git diff [--options] <commit>..<commit> [--] [<path>...]
This is synonymous to the previous form. If <commit> on one side is omitted, it
will have the same effect as using HEAD instead.
git diff [--options] <commit>...<commit> [--] [<path>...]
This form is to view the changes on the branch containing and up to the second
<commit>, starting at a common ancestor of both <commit>. "git diff A...B" is
equivalent to "git diff $(git-merge-base A B) B". You can omit any one of
<commit>, which has the same effect as using HEAD instead.
Just in case if you are doing something exotic, it should be noted that all of the
<commit> in the above description, except in the last two forms that use ".."
notations, can be any <tree>.
For a more complete list of ways to spell <commit>, see "SPECIFYING REVISIONS"
section in gitrevisions(7). However, "diff" is about comparing two endpoints, not
ranges, and the range notations ("<commit>..<commit>" and "<commit>...<commit>") do
not mean a range as defined in the "SPECIFYING RANGES" section in gitrevisions(7).
git diff [options] <blob> <blob>
This form is to view the differences between the raw contents of two blob
objects.
OPTIONS
-p, -u, --patch
git diff [options] <blob> <blob>
This form is to view the differences between the raw contents of two blob
objects.
OPTIONS
-p, -u, --patch
Generate patch (see section on generating patches). This is the default.
-s, --no-patch
Suppress diff output. Useful for commands like git show that show the patch by
default, or to cancel the effect of --patch.
-U<n>, --unified=<n>
Generate diffs with <n> lines of context instead of the usual three. Implies
-p.
--raw
Generate the diff in raw format.
--patch-with-raw
Synonym for -p --raw.
--indent-heuristic
Enable the heuristic that shift diff hunk boundaries to make patches easier to
read. This is the default.
--no-indent-heuristic
Disable the indent heuristic.
--minimal
Spend extra time to make sure the smallest possible diff is produced.
--patience
Generate a diff using the "patience diff" algorithm.
--histogram
Generate a diff using the "histogram diff" algorithm.
--anchored=<text>
Generate a diff using the "anchored diff" algorithm.
This option may be specified more than once.
If a line exists in both the source and destination, exists only once, and
starts with this text, this algorithm attempts to prevent it from appearing as
a deletion or addition in the output. It uses the "patience diff" algorithm
internally.
--diff-algorithm={patience|minimal|histogram|myers}
Choose a diff algorithm. The variants are as follows:
default, myers
The basic greedy diff algorithm. Currently, this is the default.
minimal
Spend extra time to make sure the smallest possible diff is produced.
patience
Use "patience diff" algorithm when generating patches.
histogram
This algorithm extends the patience algorithm to "support low-occurrence
common elements".
For instance, if you configured diff.algorithm variable to a non-default value
and want to use the default one, then you have to use --diff-algorithm=default
option.
--stat[=<width>[,<name-width>[,<count>]]]
Generate a diffstat. By default, as much space as necessary will be used for
the filename part, and the rest for the graph part. Maximum width defaults to
terminal width, or 80 columns if not connected to a terminal, and can be
overridden by <width>. The width of the filename part can be limited by giving
another width <name-width> after a comma. The width of the graph part can be
limited by using --stat-graph-width=<width> (affects all commands generating a
stat graph) or by setting diff.statGraphWidth=<width> (does not affect git
format-patch). By giving a third parameter <count>, you can limit the output to
the first <count> lines, followed by ... if there are more.
These parameters can also be set individually with --stat-width=<width>,
--stat-name-width=<name-width> and --stat-count=<count>.
--numstat
Similar to --stat, but shows number of added and deleted lines in decimal
notation and pathname without abbreviation, to make it more machine friendly.
For binary files, outputs two - instead of saying 0 0.
--shortstat
Output only the last line of the --stat format containing total number of
modified files, as well as number of added and deleted lines.
--dirstat[=<param1,param2,...>]
Output the distribution of relative amount of changes for each sub-directory.
The behavior of --dirstat can be customized by passing it a comma separated
list of parameters. The defaults are controlled by the diff.dirstat
configuration variable (see git-config(1)). The following parameters are
available:
changes
Compute the dirstat numbers by counting the lines that have been removed
from the source, or added to the destination. This ignores the amount of
pure code movements within a file. In other words, rearranging lines in a
file is not counted as much as other changes. This is the default behavior
when no parameter is given.
lines
Compute the dirstat numbers by doing the regular line-based diff analysis,
and summing the removed/added line counts. (For binary files, count 64-byte
chunks instead, since binary files have no natural concept of lines). This
is a more expensive --dirstat behavior than the changes behavior, but it
does count rearranged lines within a file as much as other changes. The
resulting output is consistent with what you get from the other --*stat
options.
files
Compute the dirstat numbers by counting the number of files changed. Each
changed file counts equally in the dirstat analysis. This is the
computationally cheapest --dirstat behavior, since it does not have to look
at the file contents at all.
cumulative
Count changes in a child directory for the parent directory as well. Note
that when using cumulative, the sum of the percentages reported may exceed
100%. The default (non-cumulative) behavior can be specified with the
noncumulative parameter.
<limit>
An integer parameter specifies a cut-off percent (3% by default).
Directories contributing less than this percentage of the changes are not
shown in the output.
Example: The following will count changed files, while ignoring directories
with less than 10% of the total amount of changed files, and accumulating child
directory counts in the parent directories: --dirstat=files,10,cumulative.
--summary
Output a condensed summary of extended header information such as creations,
renames and mode changes.
--patch-with-stat
Synonym for -p --stat.
-z
When --raw, --numstat, --name-only or --name-status has been given, do not
munge pathnames and use NULs as output field terminators.
Without this option, pathnames with "unusual" characters are quoted as
explained for the configuration variable core.quotePath (see git-config(1)).
--name-only
Show only names of changed files.
--name-status
Show only names and status of changed files. See the description of the
--diff-filter option on what the status letters mean.
--submodule[=<format>]
Specify how differences in submodules are shown. When specifying
--submodule=short the short format is used. This format just shows the names of
the commits at the beginning and end of the range. When --submodule or
--submodule=log is specified, the log format is used. This format lists the
commits in the range like git-submodule(1) summary does. When --submodule=diff
is specified, the diff format is used. This format shows an inline diff of the
changes in the submodule contents between the commit range. Defaults to
diff.submodule or the short format if the config option is unset.
--color[=<when>]
Show colored diff. --color (i.e. without =<when>) is the same as
--color=always. <when> can be one of always, never, or auto. It can be changed
by the color.ui and color.diff configuration settings.
--no-color
Turn off colored diff. This can be used to override configuration settings. It
is the same as --color=never.
--color-moved[=<mode>]
Moved lines of code are colored differently. It can be changed by the
diff.colorMoved configuration setting. The <mode> defaults to no if the option
is not given and to zebra if the option with no mode is given. The mode must be
one of:
no
Moved lines are not highlighted.
default
Is a synonym for zebra. This may change to a more sensible mode in the
future.
plain
Any line that is added in one location and was removed in another location
will be colored with color.diff.newMoved. Similarly color.diff.oldMoved
will be used for removed lines that are added somewhere else in the diff.
This mode picks up any moved line, but it is not very useful in a review to
determine if a block of code was moved without permutation.
zebra
Blocks of moved text of at least 20 alphanumeric characters are detected
greedily. The detected blocks are painted using either the
color.diff.{old,new}Moved color or color.diff.{old,new}MovedAlternative.
The change between the two colors indicates that a new block was detected.
dimmed_zebra
Similar to zebra, but additional dimming of uninteresting parts of moved
code is performed. The bordering lines of two adjacent blocks are
considered interesting, the rest is uninteresting.
--word-diff[=<mode>]
Show a word diff, using the <mode> to delimit changed words. By default, words
are delimited by whitespace; see --word-diff-regex below. The <mode> defaults
to plain, and must be one of:
color
Highlight changed words using only colors. Implies --color.
plain
Show words as [-removed-] and {+added+}. Makes no attempts to escape the
delimiters if they appear in the input, so the output may be ambiguous.
porcelain
Use a special line-based format intended for script consumption.
Added/removed/unchanged runs are printed in the usual unified diff format,
starting with a +/-/` ` character at the beginning of the line and
extending to the end of the line. Newlines in the input are represented by
a tilde ~ on a line of its own.
none
Disable word diff again.
Note that despite the name of the first mode, color is used to highlight the
changed parts in all modes if enabled.
--word-diff-regex=<regex>
Use <regex> to decide what a word is, instead of considering runs of
non-whitespace to be a word. Also implies --word-diff unless it was already
enabled.
Every non-overlapping match of the <regex> is considered a word. Anything
between these matches is considered whitespace and ignored(!) for the purposes
of finding differences. You may want to append |[^[:space:]] to your regular
expression to make sure that it matches all non-whitespace characters. A match
that contains a newline is silently truncated(!) at the newline.
For example, --word-diff-regex=. will treat each character as a word and,
correspondingly, show differences character by character.
The regex can also be set via a diff driver or configuration option, see
gitattributes(5) or git-config(1). Giving it explicitly overrides any diff
driver or configuration setting. Diff drivers override configuration settings.
--color-words[=<regex>]
Equivalent to --word-diff=color plus (if a regex was specified)
--word-diff-regex=<regex>.
--no-renames
Turn off rename detection, even when the configuration file gives the default
to do so.
--check
Warn if changes introduce conflict markers or whitespace errors. What are
considered whitespace errors is controlled by core.whitespace configuration. By
default, trailing whitespaces (including lines that solely consist of
whitespaces) and a space character that is immediately followed by a tab
character inside the initial indent of the line are considered whitespace
errors. Exits with non-zero status if problems are found. Not compatible with
--exit-code.
--ws-error-highlight=<kind>
Highlight whitespace errors in the context, old or new lines of the diff.
Multiple values are separated by comma, none resets previous values, default
reset the list to new and all is a shorthand for old,new,context. When this
option is not given, and the configuration variable diff.wsErrorHighlight is
not set, only whitespace errors in new lines are highlighted. The whitespace
errors are colored whith color.diff.whitespace.
--full-index
Instead of the first handful of characters, show the full pre- and post-image
blob object names on the "index" line when generating patch format output.
--binary
In addition to --full-index, output a binary diff that can be applied with
git-apply.
--abbrev[=<n>]
Instead of showing the full 40-byte hexadecimal object name in diff-raw format
output and diff-tree header lines, show only a partial prefix. This is
independent of the --full-index option above, which controls the diff-patch
output format. Non default number of digits can be specified with --abbrev=<n>.
-B[<n>][/<m>], --break-rewrites[=[<n>][/<m>]]
Break complete rewrite changes into pairs of delete and create. This serves two
purposes:
It affects the way a change that amounts to a total rewrite of a file not as a
series of deletion and insertion mixed together with a very few lines that
happen to match textually as the context, but as a single deletion of
everything old followed by a single insertion of everything new, and the number
m controls this aspect of the -B option (defaults to 60%). -B/70% specifies
that less than 30% of the original should remain in the result for Git to
consider it a total rewrite (i.e. otherwise the resulting patch will be a
series of deletion and insertion mixed together with context lines).
When used with -M, a totally-rewritten file is also considered as the source of
a rename (usually -M only considers a file that disappeared as the source of a
rename), and the number n controls this aspect of the -B option (defaults to
50%). -B20% specifies that a change with addition and deletion compared to 20%
or more of the file's size are eligible for being picked up as a possible
source of a rename to another file.
-M[<n>], --find-renames[=<n>]
Detect renames. If n is specified, it is a threshold on the similarity index
(i.e. amount of addition/deletions compared to the file's size). For example,
-M90% means Git should consider a delete/add pair to be a rename if more than
90% of the file hasn't changed. Without a % sign, the number is to be read as a
fraction, with a decimal point before it. I.e., -M5 becomes 0.5, and is thus
the same as -M50%. Similarly, -M05 is the same as -M5%. To limit detection to
exact renames, use -M100%. The default similarity index is 50%.
-C[<n>], --find-copies[=<n>]
Detect copies as well as renames. See also --find-copies-harder. If n is
specified, it has the same meaning as for -M<n>.
--find-copies-harder
For performance reasons, by default, -C option finds copies only if the
original file of the copy was modified in the same changeset. This flag makes
the command inspect unmodified files as candidates for the source of copy. This
is a very expensive operation for large projects, so use it with caution.
Giving more than one -C option has the same effect.
-D, --irreversible-delete
Omit the preimage for deletes, i.e. print only the header but not the diff
between the preimage and /dev/null. The resulting patch is not meant to be
applied with patch or git apply; this is solely for people who want to just
concentrate on reviewing the text after the change. In addition, the output
obviously lacks enough information to apply such a patch in reverse, even
manually, hence the name of the option.
When used together with -B, omit also the preimage in the deletion part of a
delete/create pair.
-l<num>
The -M and -C options require O(n^2) processing time where n is the number of
potential rename/copy targets. This option prevents rename/copy detection from
running if the number of rename/copy targets exceeds the specified number.
--diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]
Select only files that are Added (A), Copied (C), Deleted (D), Modified (M),
Renamed (R), have their type (i.e. regular file, symlink, submodule, ...)
changed (T), are Unmerged (U), are Unknown (X), or have had their pairing
Broken (B). Any combination of the filter characters (including none) can be
used. When * (All-or-none) is added to the combination, all paths are selected
if there is any file that matches other criteria in the comparison; if there is
no file that matches other criteria, nothing is selected.
Also, these upper-case letters can be downcased to exclude. E.g.
--diff-filter=ad excludes added and deleted paths.
Note that not all diffs can feature all types. For instance, diffs from the
index to the working tree can never have Added entries (because the set of
paths included in the diff is limited by what is in the index). Similarly,
copied and renamed entries cannot appear if detection for those types is
disabled.
-S<string>
Look for differences that change the number of occurrences of the specified
string (i.e. addition/deletion) in a file. Intended for the scripter's use.
It is useful when you're looking for an exact block of code (like a struct),
and want to know the history of that block since it first came into being: use
the feature iteratively to feed the interesting block in the preimage back into
-S, and keep going until you get the very first version of the block.
-G<regex>
Look for differences whose patch text contains added/removed lines that match
<regex>.
To illustrate the difference between -S<regex> --pickaxe-regex and -G<regex>,
consider a commit with the following diff in the same file:
+ return !regexec(regexp, two->ptr, 1, ®match, 0);
...
- hit = !regexec(regexp, mf2.ptr, 1, ®match, 0);
While git log -G"regexec(regexp" will show this commit, git log
-S"regexec(regexp" --pickaxe-regex will not (because the number of occurrences
of that string did not change).
See the pickaxe entry in gitdiffcore(7) for more information.
--pickaxe-all
When -S or -G finds a change, show all the changes in that changeset, not just
the files that contain the change in <string>.
--pickaxe-regex
Treat the <string> given to -S as an extended POSIX regular expression to
match.
-O<orderfile>
Control the order in which files appear in the output. This overrides the
diff.orderFile configuration variable (see git-config(1)). To cancel
diff.orderFile, use -O/dev/null.
The output order is determined by the order of glob patterns in <orderfile>.
All files with pathnames that match the first pattern are output first, all
files with pathnames that match the second pattern (but not the first) are
output next, and so on. All files with pathnames that do not match any pattern
are output last, as if there was an implicit match-all pattern at the end of
the file. If multiple pathnames have the same rank (they match the same pattern
but no earlier patterns), their output order relative to each other is the
normal order.
<orderfile> is parsed as follows:
o Blank lines are ignored, so they can be used as separators for readability.
o Lines starting with a hash ("#") are ignored, so they can be used for
comments. Add a backslash ("") to the beginning of the pattern if it
starts with a hash.
o Each other line contains a single pattern.
Patterns have the same syntax and semantics as patterns used for fnmantch(3)
without the FNM_PATHNAME flag, except a pathname also matches a pattern if
removing any number of the final pathname components matches the pattern. For
example, the pattern "foo*bar" matches "fooasdfbar" and "foo/bar/baz/asdf" but
not "foobarx".
-R
Swap two inputs; that is, show differences from index or on-disk file to tree
contents.
--relative[=<path>]
When run from a subdirectory of the project, it can be told to exclude changes
outside the directory and show pathnames relative to it with this option. When
you are not in a subdirectory (e.g. in a bare repository), you can name which
subdirectory to make the output relative to by giving a <path> as an argument.
-a, --text
Treat all files as text.
--ignore-cr-at-eol
Ignore carrige-return at the end of line when doing a comparison.
--ignore-space-at-eol
Ignore changes in whitespace at EOL.
-b, --ignore-space-change
Ignore changes in amount of whitespace. This ignores whitespace at line end,
and considers all other sequences of one or more whitespace characters to be
equivalent.
-w, --ignore-all-space
Ignore whitespace when comparing lines. This ignores differences even if one
line has whitespace where the other line has none.
--ignore-blank-lines
Ignore changes whose lines are all blank.
--inter-hunk-context=<lines>
Show the context between diff hunks, up to the specified number of lines,
thereby fusing hunks that are close to each other. Defaults to
diff.interHunkContext or 0 if the config option is unset.
-W, --function-context
Show whole surrounding functions of changes.
--exit-code
Make the program exit with codes similar to diff(1). That is, it exits with 1
if there were differences and 0 means no differences.
--quiet
Disable all output of the program. Implies --exit-code.
--ext-diff
Allow an external diff helper to be executed. If you set an external diff
driver with gitattributes(5), you need to use this option with git-log(1) and
friends.
--no-ext-diff
Disallow external diff drivers.
--textconv, --no-textconv
Allow (or disallow) external text conversion filters to be run when comparing
binary files. See gitattributes(5) for details. Because textconv filters are
typically a one-way conversion, the resulting diff is suitable for human
consumption, but cannot be applied. For this reason, textconv filters are
enabled by default only for git-diff(1) and git-log(1), but not for git-format-
patch(1) or diff plumbing commands.
--ignore-submodules[=<when>]
Ignore changes to submodules in the diff generation. <when> can be either
"none", "untracked", "dirty" or "all", which is the default. Using "none" will
consider the submodule modified when it either contains untracked or modified
files or its HEAD differs from the commit recorded in the superproject and can
be used to override any settings of the ignore option in git-config(1) or
gitmodules(5). When "untracked" is used submodules are not considered dirty
when they only contain untracked content (but they are still scanned for
modified content). Using "dirty" ignores all changes to the work tree of
submodules, only changes to the commits stored in the superproject are shown
(this was the behavior until 1.7.0). Using "all" hides all changes to
submodules.
--src-prefix=<prefix>
Show the given source prefix instead of "a/".
--dst-prefix=<prefix>
Show the given destination prefix instead of "b/".
--no-prefix
Do not show any source or destination prefix.
--line-prefix=<prefix>
Prepend an additional prefix to every line of output.
--ita-invisible-in-index
By default entries added by "git add -N" appear as an existing empty file in
"git diff" and a new file in "git diff --cached". This option makes the entry
appear as a new file in "git diff" and non-existent in "git diff --cached".
This option could be reverted with --ita-visible-in-index. Both options are
experimental and could be removed in future.
For more detailed explanation on these common options, see also gitdiffcore(7).
-1 --base, -2 --ours, -3 --theirs
Compare the working tree with the "base" version (stage #1), "our branch"
(stage #2) or "their branch" (stage #3). The index contains these stages only
for unmerged entries i.e. while resolving conflicts. See git-read-tree(1)
section "3-Way Merge" for detailed information.
-0
Omit diff output for unmerged entries and just show "Unmerged". Can be used
only when comparing the working tree with the index.
<path>...
The <paths> parameters, when given, are used to limit the diff to the named
paths (you can give directory names and get diff for all files under them).
RAW OUTPUT FORMAT
The raw output format from "git-diff-index", "git-diff-tree", "git-diff-files" and
"git diff --raw" are very similar.
These commands all compare two sets of things; what is compared differs:
git-diff-index <tree-ish>
compares the <tree-ish> and the files on the filesystem.
git-diff-index --cached <tree-ish>
compares the <tree-ish> and the index.
git-diff-tree [-r] <tree-ish-1> <tree-ish-2> [<pattern>...]
compares the trees named by the two arguments.
git-diff-files [<pattern>...]
compares the index and the files on the filesystem.
The "git-diff-tree" command begins its output by printing the hash of what is being
compared. After that, all the commands print one output line per changed file.
An output line is formatted this way:
in-place edit :100644 100644 bcd1234... 0123456... M file0
copy-edit :100644 100644 abcd123... 1234567... C68 file1 file2
rename-edit :100644 100644 abcd123... 1234567... R86 file1 file3
create :000000 100644 0000000... 1234567... A file4
delete :100644 000000 1234567... 0000000... D file5
unmerged :000000 000000 0000000... 0000000... U file6
That is, from the left to the right:
1. a colon.
2. mode for "src"; 000000 if creation or unmerged.
3. a space.
4. mode for "dst"; 000000 if deletion or unmerged.
5. a space.
6. sha1 for "src"; 0{40} if creation or unmerged.
7. a space.
8. sha1 for "dst"; 0{40} if creation, unmerged or "look at work tree".
9. a space.
10. status, followed by optional "score" number.
11. a tab or a NUL when -z option is used.
12. path for "src"
13. a tab or a NUL when -z option is used; only exists for C or R.
14. path for "dst"; only exists for C or R.
15. an LF or a NUL when -z option is used, to terminate the record.
Possible status letters are:
o A: addition of a file
o C: copy of a file into a new one
o D: deletion of a file
o M: modification of the contents or mode of a file
o R: renaming of a file
o T: change in the type of the file
o U: file is unmerged (you must complete the merge before it can be committed)
o X: "unknown" change type (most probably a bug, please report it)
Status letters C and R are always followed by a score (denoting the percentage of
similarity between the source and target of the move or copy). Status letter M may
be followed by a score (denoting the percentage of dissimilarity) for file
rewrites.
<sha1> is shown as all 0's if a file is new on the filesystem and it is out of sync
with the index.
Example:
:100644 100644 5be4a4...... 000000...... M file.c
Without the -z option, pathnames with "unusual" characters are quoted as explained
for the configuration variable core.quotePath (see git-config(1)). Using -z the
filename is output verbatim and the line is terminated by a NUL byte.
DIFF FORMAT FOR MERGES
"git-diff-tree", "git-diff-files" and "git-diff --raw" can take -c or --cc option
to generate diff output also for merge commits. The output differs from the format
described above in the following way:
1. there is a colon for each parent
2. there are more "src" modes and "src" sha1
3. status is concatenated status characters for each parent
4. no optional "score" number
5. single path, only for "dst"
Example:
::100644 100644 100644 fabadb8... cc95eb0... 4866510... MM describe.c
Note that combined diff lists only files which were modified from all parents.
GENERATING PATCHES WITH -P
When "git-diff-index", "git-diff-tree", or "git-diff-files" are run with a -p
option, "git diff" without the --raw option, or "git log" with the "-p" option,
they do not produce the output described above; instead they produce a patch file.
You can customize the creation of such patches via the GIT_EXTERNAL_DIFF and the
GIT_DIFF_OPTS environment variables.
What the -p option produces is slightly different from the traditional diff format:
1. It is preceded with a "git diff" header that looks like this:
diff --git a/file1 b/file2
The a/ and b/ filenames are the same unless rename/copy is involved.
Especially, even for a creation or a deletion, /dev/null is not used in place
of the a/ or b/ filenames.
When rename/copy is involved, file1 and file2 show the name of the source file
of the rename/copy and the name of the file that rename/copy produces,
respectively.
2. It is followed by one or more extended header lines:
old mode <mode>
new mode <mode>
deleted file mode <mode>
new file mode <mode>
copy from <path>
copy to <path>
rename from <path>
rename to <path>
similarity index <number>
dissimilarity index <number>
index <hash>..<hash> <mode>
File modes are printed as 6-digit octal numbers including the file type and
file permission bits.
Path names in extended headers do not include the a/ and b/ prefixes.
The similarity index is the percentage of unchanged lines, and the
dissimilarity index is the percentage of changed lines. It is a rounded down
integer, followed by a percent sign. The similarity index value of 100% is thus
reserved for two equal files, while 100% dissimilarity means that no line from
the old file made it into the new one.
The index line includes the SHA-1 checksum before and after the change. The
<mode> is included if the file mode does not change; otherwise, separate lines
indicate the old and the new mode.
3. Pathnames with "unusual" characters are quoted as explained for the
configuration variable core.quotePath (see git-config(1)).
4. All the file1 files in the output refer to files before the commit, and all the
file2 files refer to files after the commit. It is incorrect to apply each
change to each file sequentially. For example, this patch will swap a and b:
diff --git a/a b/b
rename from a
rename to b
diff --git a/b b/a
rename from b
rename to a
COMBINED DIFF FORMAT
Any diff-generating command can take the -c or --cc option to produce a combined
diff when showing a merge. This is the default format when showing merges with git-
diff(1) or git-show(1). Note also that you can give the -m option to any of these
commands to force generation of diffs with individual parents of a merge.
A combined diff format looks like this:
diff --combined describe.c
index fabadb8,cc95eb0..4866510
--- a/describe.c
+++ b/describe.c
@@@ -98,20 -98,12 +98,20 @@@
return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
}
- static void describe(char *arg)
-static void describe(struct commit *cmit, int last_one)
++static void describe(char *arg, int last_one)
{
+ unsigned char sha1[20];
+ struct commit *cmit;
struct commit_list *list;
static int initialized = 0;
struct commit_name *n;
+ if (get_sha1(arg, sha1) < 0)
+ usage(describe_usage);
+ cmit = lookup_commit_reference(sha1);
+ if (!cmit)
+ usage(describe_usage);
+
if (!initialized) {
initialized = 1;
for_each_ref(get_name);
1. It is preceded with a "git diff" header, that looks like this (when -c option
is used):
diff --combined file
or like this (when --cc option is used):
diff --cc file
2. It is followed by one or more extended header lines (this example shows a merge
with two parents):
index <hash>,<hash>..<hash>
mode <mode>,<mode>..<mode>
new file mode <mode>
deleted file mode <mode>,<mode>
The mode <mode>,<mode>..<mode> line appears only if at least one of the <mode>
is different from the rest. Extended headers with information about detected
contents movement (renames and copying detection) are designed to work with
diff of two <tree-ish> and are not used by combined diff format.
3. It is followed by two-line from-file/to-file header
--- a/file
+++ b/file
Similar to two-line header for traditional unified diff format, /dev/null is
used to signal created or deleted files.
4. Chunk header format is modified to prevent people from accidentally feeding it
to patch -p1. Combined diff format was created for review of merge commit
changes, and was not meant for apply. The change is similar to the change in
the extended index header:
@@@ <from-file-range> <from-file-range> <to-file-range> @@@
There are (number of parents + 1) @ characters in the chunk header for combined
diff format.
Unlike the traditional unified diff format, which shows two files A and B with a
single column that has - (minus -- appears in A but removed in B), + (plus --
missing in A but added to B), or " " (space -- unchanged) prefix, this format
compares two or more files file1, file2,... with one file X, and shows how X
differs from each of fileN. One column for each of fileN is prepended to the output
line to note how X's line is different from it.
A - character in the column N means that the line appears in fileN but it does not
appear in the result. A + character in the column N means that the line appears in
the result, and fileN does not have that line (in other words, the line was added,
from the point of view of that parent).
In the above example output, the function signature was changed from both files
(hence two - removals from both file1 and file2, plus ++ to mean one line that was
added does not appear in either file1 or file2). Also eight other lines are the
same from file1 but do not appear in file2 (hence prefixed with +).
When shown by git diff-tree -c, it compares the parents of a merge commit with the
merge result (i.e. file1..fileN are the parents). When shown by git diff-files -c,
it compares the two unresolved merge parents with the working tree file (i.e. file1
is stage 2 aka "our version", file2 is stage 3 aka "their version").
OTHER DIFF FORMATS
The --summary option describes newly added, deleted, renamed and copied files. The
--stat option adds diffstat(1) graph to the output. These options can be combined
with other options, such as -p, and are meant for human consumption.
When showing a change that involves a rename or a copy, --stat output formats the
pathnames compactly by combining common prefix and suffix of the pathnames. For
example, a change that moves arch/i386/Makefile to arch/x86/Makefile while
modifying 4 lines will be shown like this:
arch/{i386 => x86}/Makefile | 4 +--
The --numstat option gives the diffstat(1) information but is designed for easier
machine consumption. An entry in --numstat output looks like this:
1 2 README
3 1 arch/{i386 => x86}/Makefile
That is, from left to right:
1. the number of added lines;
2. a tab;
3. the number of deleted lines;
4. a tab;
5. pathname (possibly with rename/copy information);
6. a newline.
When -z output option is in effect, the output is formatted this way:
1 2 README NUL
3 1 NUL arch/i386/Makefile NUL arch/x86/Makefile NUL
That is:
1. the number of added lines;
2. a tab;
3. the number of deleted lines;
4. a tab;
5. a NUL (only exists if renamed/copied);
6. pathname in preimage;
7. a NUL (only exists if renamed/copied);
8. pathname in postimage (only exists if renamed/copied);
9. a NUL.
The extra NUL before the preimage path in renamed case is to allow scripts that
read the output to tell if the current record being read is a single-path record or
a rename/copy record without reading ahead. After reading added and deleted lines,
reading up to NUL would yield the pathname, but if that is NUL, the record will
show two paths.
EXAMPLES
Various ways to check your working tree
$ git diff (1)
$ git diff --cached (2)
$ git diff HEAD (3)
1. Changes in the working tree not yet staged for the next commit.
2. Changes between the index and your last commit; what you would be committing
if you run "git commit" without "-a" option.
3. Changes in the working tree since your last commit; what you would be
committing if you run "git commit -a"
Comparing with arbitrary commits
$ git diff test (1)
$ git diff HEAD -- ./test (2)
$ git diff HEAD^ HEAD (3)
1. Instead of using the tip of the current branch, compare with the tip of
"test" branch.
2. Instead of comparing with the tip of "test" branch, compare with the tip of
the current branch, but limit the comparison to the file "test".
3. Compare the version before the last commit and the last commit.
Comparing branches
$ git diff topic master (1)
$ git diff topic..master (2)
$ git diff topic...master (3)
1. Changes between the tips of the topic and the master branches.
2. Same as above.
3. Changes that occurred on the master branch since when the topic branch was
started off it.