contrib: add 'git difftool' for launching common merge tools

'git difftool' is a git command that allows you to compare and edit files
between revisions using common merge tools.  'git difftool' does what
'git mergetool' does but its use is for non-merge situations such as
when preparing commits or comparing changes against the index.
It uses the same configuration variables as 'git mergetool' and
provides the same command-line interface as 'git diff'.

Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/contrib/difftool/git-difftool.txt b/contrib/difftool/git-difftool.txt
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+git-difftool(1)
+===============
+
+NAME
+----
+git-difftool - compare changes using common merge tools
+
+SYNOPSIS
+--------
+'git difftool' [--tool=<tool>] [--no-prompt] ['git diff' options]
+
+DESCRIPTION
+-----------
+'git difftool' is a git command that allows you to compare and edit files
+between revisions using common merge tools.  At its most basic level,
+'git difftool' does what 'git mergetool' does but its use is for non-merge
+situations such as when preparing commits or comparing changes against
+the index.
+
+'git difftool' is a frontend to 'git diff' and accepts the same
+arguments and options.
+
+See linkgit:git-diff[7] for the full list of supported options.
+
+OPTIONS
+-------
+-t <tool>::
+--tool=<tool>::
+	Use the merge resolution program specified by <tool>.
+	Valid merge tools are:
+	kdiff3, tkdiff, meld, xxdiff, emerge, vimdiff, gvimdiff, ecmerge, and opendiff
++
+If a merge resolution program is not specified, 'git difftool'
+will use the configuration variable `merge.tool`.  If the
+configuration variable `merge.tool` is not set, 'git difftool'
+will pick a suitable default.
++
+You can explicitly provide a full path to the tool by setting the
+configuration variable `mergetool.<tool>.path`. For example, you
+can configure the absolute path to kdiff3 by setting
+`mergetool.kdiff3.path`. Otherwise, 'git difftool' assumes the
+tool is available in PATH.
++
+Instead of running one of the known merge tool programs,
+'git difftool' can be customized to run an alternative program
+by specifying the command line to invoke in a configuration
+variable `mergetool.<tool>.cmd`.
++
+When 'git difftool' is invoked with this tool (either through the
+`-t` or `--tool` option or the `merge.tool` configuration variable)
+the configured command line will be invoked with the following
+variables available: `$LOCAL` is set to the name of the temporary
+file containing the contents of the diff pre-image and `$REMOTE`
+is set to the name of the temporary file containing the contents
+of the diff post-image.  `$BASE` is provided for compatibility
+with custom merge tool commands and has the same value as `$LOCAL`.
+
+--no-prompt::
+	Do not prompt before launching a merge tool.
+
+CONFIG VARIABLES
+----------------
+merge.tool::
+	The default merge tool to use.
++
+See the `--tool=<tool>` option above for more details.
+
+merge.keepBackup::
+	The original, unedited file content can be saved to a file with
+	a `.orig` extension.  Defaults to `true` (i.e. keep the backup files).
+
+mergetool.<tool>.path::
+	Override the path for the given tool.  This is useful in case
+	your tool is not in the PATH.
+
+mergetool.<tool>.cmd::
+	Specify the command to invoke the specified merge tool.
++
+See the `--tool=<tool>` option above for more details.
+
+
+SEE ALSO
+--------
+linkgit:git-diff[7]::
+	 Show changes between commits, commit and working tree, etc
+
+linkgit:git-mergetool[1]::
+	Run merge conflict resolution tools to resolve merge conflicts
+
+linkgit:git-config[7]::
+	 Get and set repository or global options
+
+
+AUTHOR
+------
+Written by David Aguilar <davvid@gmail.com>.
+
+Documentation
+--------------
+Documentation by David Aguilar and the git-list <git@vger.kernel.org>.
+
+GIT
+---
+Part of the linkgit:git[1] suite