git/Documentation/diff-config.txt
Johan Herland 1c57a627bf New --dirstat=lines mode, doing dirstat analysis based on diffstat
This patch adds an alternative implementation of show_dirstat(), called
show_dirstat_by_line(), which uses the more expensive diffstat analysis
(as opposed to show_dirstat()'s own (relatively inexpensive) analysis)
to derive the numbers from which the --dirstat output is computed.

The alternative implementation is controlled by the new "lines" parameter
to the --dirstat option (or the diff.dirstat config variable).

For binary files, the diffstat analysis counts bytes instead of lines,
so to prevent binary files from dominating the dirstat results, the
byte counts for binary files are divided by 64 before being compared to
their textual/line-based counterparts. This is a stupid and ugly - but
very cheap - heuristic.

In linux-2.6.git, running the three different --dirstat modes:

  time git diff v2.6.20..v2.6.30 --dirstat=changes > /dev/null
vs.
  time git diff v2.6.20..v2.6.30 --dirstat=lines > /dev/null
vs.
  time git diff v2.6.20..v2.6.30 --dirstat=files > /dev/null

yields the following average runtimes on my machine:

 - "changes" (default): ~6.0 s
 - "lines":             ~9.6 s
 - "files":             ~0.1 s

So, as expected, there's a considerable performance hit (~60%) by going
through the full diffstat analysis as compared to the default "changes"
analysis (obviously, "files" is much faster than both). As such, the
"lines" mode is probably only useful if you really need the --dirstat
numbers to be consistent with the numbers returned from the other
--*stat options.

The patch also includes documentation and tests for the new dirstat mode.

Improved-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-04-29 11:22:55 -07:00

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diff.autorefreshindex::
When using 'git diff' to compare with work tree
files, do not consider stat-only change as changed.
Instead, silently run `git update-index --refresh` to
update the cached stat information for paths whose
contents in the work tree match the contents in the
index. This option defaults to true. Note that this
affects only 'git diff' Porcelain, and not lower level
'diff' commands such as 'git diff-files'.
diff.dirstat::
A comma separated list of `--dirstat` parameters specifying the
default behavior of the `--dirstat` option to linkgit:git-diff[1]`
and friends. The defaults can be overridden on the command line
(using `--dirstat=<param1,param2,...>`). The fallback defaults
(when not changed by `diff.dirstat`) are `changes,noncumulative,3`.
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:
`files,10,cumulative`.
diff.external::
If this config variable is set, diff generation is not
performed using the internal diff machinery, but using the
given command. Can be overridden with the `GIT_EXTERNAL_DIFF'
environment variable. The command is called with parameters
as described under "git Diffs" in linkgit:git[1]. Note: if
you want to use an external diff program only on a subset of
your files, you might want to use linkgit:gitattributes[5] instead.
diff.ignoreSubmodules::
Sets the default value of --ignore-submodules. Note that this
affects only 'git diff' Porcelain, and not lower level 'diff'
commands such as 'git diff-files'. 'git checkout' also honors
this setting when reporting uncommitted changes.
diff.mnemonicprefix::
If set, 'git diff' uses a prefix pair that is different from the
standard "a/" and "b/" depending on what is being compared. When
this configuration is in effect, reverse diff output also swaps
the order of the prefixes:
`git diff`;;
compares the (i)ndex and the (w)ork tree;
`git diff HEAD`;;
compares a (c)ommit and the (w)ork tree;
`git diff --cached`;;
compares a (c)ommit and the (i)ndex;
`git diff HEAD:file1 file2`;;
compares an (o)bject and a (w)ork tree entity;
`git diff --no-index a b`;;
compares two non-git things (1) and (2).
diff.noprefix::
If set, 'git diff' does not show any source or destination prefix.
diff.renameLimit::
The number of files to consider when performing the copy/rename
detection; equivalent to the 'git diff' option '-l'.
diff.renames::
Tells git to detect renames. If set to any boolean value, it
will enable basic rename detection. If set to "copies" or
"copy", it will detect copies, as well.
diff.suppressBlankEmpty::
A boolean to inhibit the standard behavior of printing a space
before each empty output line. Defaults to false.
diff.<driver>.command::
The custom diff driver command. See linkgit:gitattributes[5]
for details.
diff.<driver>.xfuncname::
The regular expression that the diff driver should use to
recognize the hunk header. A built-in pattern may also be used.
See linkgit:gitattributes[5] for details.
diff.<driver>.binary::
Set this option to true to make the diff driver treat files as
binary. See linkgit:gitattributes[5] for details.
diff.<driver>.textconv::
The command that the diff driver should call to generate the
text-converted version of a file. The result of the
conversion is used to generate a human-readable diff. See
linkgit:gitattributes[5] for details.
diff.<driver>.wordregex::
The regular expression that the diff driver should use to
split words in a line. See linkgit:gitattributes[5] for
details.
diff.<driver>.cachetextconv::
Set this option to true to make the diff driver cache the text
conversion outputs. See linkgit:gitattributes[5] for details.
diff.tool::
The diff tool to be used by linkgit:git-difftool[1]. This
option overrides `merge.tool`, and has the same valid built-in
values as `merge.tool` minus "tortoisemerge" and plus
"kompare". Any other value is treated as a custom diff tool,
and there must be a corresponding `difftool.<tool>.cmd`
option.