difftool: move 'git-difftool' out of contrib

This prepares 'git-difftool' and its documentation for
mainstream use.

'git-difftool-helper' became 'git-difftool--helper'
since users should not use it directly.

'git-difftool' was added to the list of commands as
an ancillaryinterrogator.

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

diff --git a/.gitignore b/.gitignore
index 1c57d4c958bc5e8ff539c5f5ddb1c784d923271b..a36da9d981e4153b0cd20d0737f958b3da1f4efc 100644 (file)
--- a/.gitignore
+++ b/.gitignore
@@ -35,6 +35,8 @@ git-diff
 git-diff-files
 git-diff-index
 git-diff-tree
+git-difftool
+git-difftool--helper
 git-describe
 git-fast-export
 git-fast-import

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 3afd124749fc6301069a0832071000a769e5053b..94ef1a62f98961eaa7028c1aa3bc95b9c48e85c9 100644 (file)
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -667,6 +667,24 @@ diff.suppressBlankEmpty::
        A boolean to inhibit the standard behavior of printing a space
        before each empty output line. Defaults to false.
 
+diff.tool::
+       Controls which diff tool is used.  `diff.tool` overrides
+       `merge.tool` when used by linkgit:git-difftool[1] and has
+       the same valid values as `merge.tool` minus "tortoisemerge"
+       and plus "kompare".
+
+difftool.<tool>.path::
+       Override the path for the given tool.  This is useful in case
+       your tool is not in the PATH.
+
+difftool.<tool>.cmd::
+       Specify the command to invoke the specified diff tool.
+       The specified command is evaluated in shell 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.
+
 diff.wordRegex::
        A POSIX Extended Regular Expression used to determine what is a "word"
        when performing word-by-word difference calculations.  Character

diff --git a/Documentation/git-difftool.txt b/Documentation/git-difftool.txt
new file mode 100644 (file)
index 0000000..af68466
--- /dev/null
+++ b/Documentation/git-difftool.txt
@@ -0,0 +1,97 @@
+git-difftool(1)
+===============
+
+NAME
+----
+git-difftool - Show changes using common diff tools
+
+SYNOPSIS
+--------
+'git difftool' [--tool=<tool>] [-y|--no-prompt] [<'git diff' options>]
+
+DESCRIPTION
+-----------
+'git-difftool' is a git command that allows you to compare and edit files
+between revisions using common diff tools.  'git difftool' is a frontend
+to 'git-diff' and accepts the same options and arguments.
+
+OPTIONS
+-------
+-y::
+--no-prompt::
+       Do not prompt before launching a diff tool.
+
+-t <tool>::
+--tool=<tool>::
+       Use the diff tool specified by <tool>.
+       Valid merge tools are:
+       kdiff3, kompare, tkdiff, meld, xxdiff, emerge, vimdiff, gvimdiff,
+       ecmerge, diffuse and opendiff
++
+If a diff tool is not specified, 'git-difftool'
+will use the configuration variable `diff.tool`.  If the
+configuration variable `diff.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 `difftool.<tool>.path`. For example, you
+can configure the absolute path to kdiff3 by setting
+`difftool.kdiff3.path`. Otherwise, 'git-difftool' assumes the
+tool is available in PATH.
++
+Instead of running one of the known diff tools,
+'git-difftool' can be customized to run an alternative program
+by specifying the command line to invoke in a configuration
+variable `difftool.<tool>.cmd`.
++
+When 'git-difftool' is invoked with this tool (either through the
+`-t` or `--tool` option or the `diff.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`.
+
+See linkgit:git-diff[1] for the full list of supported options.
+
+CONFIG VARIABLES
+----------------
+'git-difftool' falls back to 'git-mergetool' config variables when the
+difftool equivalents have not been defined.
+
+diff.tool::
+       The default diff tool to use.
+
+difftool.<tool>.path::
+       Override the path for the given tool.  This is useful in case
+       your tool is not in the PATH.
+
+difftool.<tool>.cmd::
+       Specify the command to invoke the specified diff tool.
++
+See the `--tool=<tool>` option above for more details.
+
+SEE ALSO
+--------
+linkgit:git-diff[1]::
+        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[1]::
+        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

diff --git a/Makefile b/Makefile
index 7867eaccdb90729aef26dc9f67a45a5a74961aae..a80055f38d8d3e080fffe0164752b5819c0379fa 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -277,6 +277,7 @@ TEST_PROGRAMS =
 
 SCRIPT_SH += git-am.sh
 SCRIPT_SH += git-bisect.sh
+SCRIPT_SH += git-difftool--helper.sh
 SCRIPT_SH += git-filter-branch.sh
 SCRIPT_SH += git-lost-found.sh
 SCRIPT_SH += git-merge-octopus.sh
@@ -296,6 +297,7 @@ SCRIPT_SH += git-submodule.sh
 SCRIPT_SH += git-web--browse.sh
 
 SCRIPT_PERL += git-add--interactive.perl
+SCRIPT_PERL += git-difftool.perl
 SCRIPT_PERL += git-archimport.perl
 SCRIPT_PERL += git-cvsexportcommit.perl
 SCRIPT_PERL += git-cvsimport.perl

diff --git a/command-list.txt b/command-list.txt
index 3583a33ee90647d8e6ded02643eb75753760d94f..fb03a2ebb5d51f46d00fad3b3f6b1794d4fdad2b 100644 (file)
--- a/command-list.txt
+++ b/command-list.txt
@@ -33,6 +33,7 @@ git-diff                                mainporcelain common
 git-diff-files                          plumbinginterrogators
 git-diff-index                          plumbinginterrogators
 git-diff-tree                           plumbinginterrogators
+git-difftool                            ancillaryinterrogators
 git-fast-export                                ancillarymanipulators
 git-fast-import                                ancillarymanipulators
 git-fetch                               mainporcelain common

diff --git a/contrib/difftool/git-difftool b/contrib/difftool/git-difftool
deleted file mode 100755 (executable)
index 8c160e5..0000000
--- a/contrib/difftool/git-difftool
+++ /dev/null
@@ -1,76 +0,0 @@
-#!/usr/bin/env perl
-# Copyright (c) 2009 David Aguilar
-#
-# This is a wrapper around the GIT_EXTERNAL_DIFF-compatible
-# git-difftool-helper script.  This script exports
-# GIT_EXTERNAL_DIFF and GIT_PAGER for use by git, and
-# GIT_DIFFTOOL_NO_PROMPT and GIT_DIFF_TOOL for use by git-difftool-helper.
-# Any arguments that are unknown to this script are forwarded to 'git diff'.
-
-use strict;
-use warnings;
-use Cwd qw(abs_path);
-use File::Basename qw(dirname);
-
-my $DIR = abs_path(dirname($0));
-
-
-sub usage
-{
-       print << 'USAGE';
-usage: git difftool [--tool=<tool>] [-y|--no-prompt] ["git diff" options]
-USAGE
-       exit 1;
-}
-
-sub setup_environment
-{
-       $ENV{PATH} = "$DIR:$ENV{PATH}";
-       $ENV{GIT_PAGER} = '';
-       $ENV{GIT_EXTERNAL_DIFF} = 'git-difftool-helper';
-}
-
-sub exe
-{
-       my $exe = shift;
-       if ($^O eq 'MSWin32' || $^O eq 'msys') {
-               return "$exe.exe";
-       }
-       return $exe;
-}
-
-sub generate_command
-{
-       my @command = (exe('git'), 'diff');
-       my $skip_next = 0;
-       my $idx = -1;
-       for my $arg (@ARGV) {
-               $idx++;
-               if ($skip_next) {
-                       $skip_next = 0;
-                       next;
-               }
-               if ($arg eq '-t' || $arg eq '--tool') {
-                       usage() if $#ARGV <= $idx;
-                       $ENV{GIT_DIFF_TOOL} = $ARGV[$idx + 1];
-                       $skip_next = 1;
-                       next;
-               }
-               if ($arg =~ /^--tool=/) {
-                       $ENV{GIT_DIFF_TOOL} = substr($arg, 7);
-                       next;
-               }
-               if ($arg eq '-y' || $arg eq '--no-prompt') {
-                       $ENV{GIT_DIFFTOOL_NO_PROMPT} = 'true';
-                       next;
-               }
-               if ($arg eq '-h' || $arg eq '--help') {
-                       usage();
-               }
-               push @command, $arg;
-       }
-       return @command
-}
-
-setup_environment();
-exec(generate_command());

diff --git a/contrib/difftool/git-difftool-helper b/contrib/difftool/git-difftool-helper
deleted file mode 100755 (executable)
index 4b0daec..0000000
--- a/contrib/difftool/git-difftool-helper
+++ /dev/null
@@ -1,221 +0,0 @@
-#!/bin/sh
-# git-difftool-helper is a GIT_EXTERNAL_DIFF-compatible diff tool launcher.
-# This script is typically launched by using the 'git difftool'
-# convenience command.
-#
-# Copyright (c) 2009 David Aguilar
-
-# Set GIT_DIFFTOOL_NO_PROMPT to bypass the per-file prompt.
-should_prompt () {
-       test -z "$GIT_DIFFTOOL_NO_PROMPT"
-}
-
-# This function prepares temporary files and launches the appropriate
-# merge tool.
-launch_merge_tool () {
-       # Merged is the filename as it appears in the work tree
-       # Local is the contents of a/filename
-       # Remote is the contents of b/filename
-       # Custom merge tool commands might use $BASE so we provide it
-       MERGED="$1"
-       LOCAL="$2"
-       REMOTE="$3"
-       BASE="$1"
-
-       # $LOCAL and $REMOTE are temporary files so prompt
-       # the user with the real $MERGED name before launching $merge_tool.
-       if should_prompt; then
-               printf "\nViewing: '$MERGED'\n"
-               printf "Hit return to launch '%s': " "$merge_tool"
-               read ans
-       fi
-
-       # Run the appropriate merge tool command
-       case "$merge_tool" in
-       kdiff3)
-               basename=$(basename "$MERGED")
-               "$merge_tool_path" --auto \
-                       --L1 "$basename (A)" \
-                       --L2 "$basename (B)" \
-                       "$LOCAL" "$REMOTE" \
-                       > /dev/null 2>&1
-               ;;
-
-       kompare)
-               "$merge_tool_path" "$LOCAL" "$REMOTE"
-               ;;
-
-       tkdiff)
-               "$merge_tool_path" "$LOCAL" "$REMOTE"
-               ;;
-
-       meld)
-               "$merge_tool_path" "$LOCAL" "$REMOTE"
-               ;;
-
-       diffuse)
-               "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
-               ;;
-
-       vimdiff)
-               "$merge_tool_path" -d -c "wincmd l" "$LOCAL" "$REMOTE"
-               ;;
-
-       gvimdiff)
-               "$merge_tool_path" -d -c "wincmd l" -f "$LOCAL" "$REMOTE"
-               ;;
-
-       xxdiff)
-               "$merge_tool_path" \
-                       -R 'Accel.Search: "Ctrl+F"' \
-                       -R 'Accel.SearchForward: "Ctrl-G"' \
-                       "$LOCAL" "$REMOTE"
-               ;;
-
-       opendiff)
-               "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
-               ;;
-
-       ecmerge)
-               "$merge_tool_path" "$LOCAL" "$REMOTE" \
-                       --default --mode=merge2 --to="$MERGED"
-               ;;
-
-       emerge)
-               "$merge_tool_path" -f emerge-files-command \
-                       "$LOCAL" "$REMOTE" "$(basename "$MERGED")"
-               ;;
-
-       *)
-               if test -n "$merge_tool_cmd"; then
-                       ( eval $merge_tool_cmd )
-               fi
-               ;;
-       esac
-}
-
-# Verifies that (difftool|mergetool).<tool>.cmd exists
-valid_custom_tool() {
-       merge_tool_cmd="$(git config difftool.$1.cmd)"
-       test -z "$merge_tool_cmd" &&
-       merge_tool_cmd="$(git config mergetool.$1.cmd)"
-       test -n "$merge_tool_cmd"
-}
-
-# Verifies that the chosen merge tool is properly setup.
-# Built-in merge tools are always valid.
-valid_tool() {
-       case "$1" in
-       kdiff3 | kompare | tkdiff | xxdiff | meld | opendiff | emerge | vimdiff | gvimdiff | ecmerge)
-               ;; # happy
-       *)
-               if ! valid_custom_tool "$1"
-               then
-                       return 1
-               fi
-               ;;
-       esac
-}
-
-# Sets up the merge_tool_path variable.
-# This handles the difftool.<tool>.path configuration.
-# This also falls back to mergetool defaults.
-init_merge_tool_path() {
-       merge_tool_path=$(git config difftool."$1".path)
-       test -z "$merge_tool_path" &&
-       merge_tool_path=$(git config mergetool."$1".path)
-       if test -z "$merge_tool_path"; then
-               case "$1" in
-               vimdiff)
-                       merge_tool_path=vim
-                       ;;
-               gvimdiff)
-                       merge_tool_path=gvim
-                       ;;
-               emerge)
-                       merge_tool_path=emacs
-                       ;;
-               *)
-                       merge_tool_path="$1"
-                       ;;
-               esac
-       fi
-}
-
-# Allow GIT_DIFF_TOOL and GIT_MERGE_TOOL to provide default values
-test -n "$GIT_MERGE_TOOL" && merge_tool="$GIT_MERGE_TOOL"
-test -n "$GIT_DIFF_TOOL" && merge_tool="$GIT_DIFF_TOOL"
-
-# If merge tool was not specified then use the diff.tool
-# configuration variable.  If that's invalid then reset merge_tool.
-# Fallback to merge.tool.
-if test -z "$merge_tool"; then
-       merge_tool=$(git config diff.tool)
-       test -z "$merge_tool" &&
-       merge_tool=$(git config merge.tool)
-       if test -n "$merge_tool" && ! valid_tool "$merge_tool"; then
-               echo >&2 "git config option diff.tool set to unknown tool: $merge_tool"
-               echo >&2 "Resetting to default..."
-               unset merge_tool
-       fi
-fi
-
-# Try to guess an appropriate merge tool if no tool has been set.
-if test -z "$merge_tool"; then
-       # We have a $DISPLAY so try some common UNIX merge tools
-       if test -n "$DISPLAY"; then
-               # If gnome then prefer meld, otherwise, prefer kdiff3 or kompare
-               if test -n "$GNOME_DESKTOP_SESSION_ID" ; then
-                       merge_tool_candidates="meld kdiff3 kompare tkdiff xxdiff gvimdiff diffuse"
-               else
-                       merge_tool_candidates="kdiff3 kompare tkdiff xxdiff meld gvimdiff diffuse"
-               fi
-       fi
-       if echo "${VISUAL:-$EDITOR}" | grep 'emacs' > /dev/null 2>&1; then
-               # $EDITOR is emacs so add emerge as a candidate
-               merge_tool_candidates="$merge_tool_candidates emerge opendiff vimdiff"
-       elif echo "${VISUAL:-$EDITOR}" | grep 'vim' > /dev/null 2>&1; then
-               # $EDITOR is vim so add vimdiff as a candidate
-               merge_tool_candidates="$merge_tool_candidates vimdiff opendiff emerge"
-       else
-               merge_tool_candidates="$merge_tool_candidates opendiff emerge vimdiff"
-       fi
-       echo "merge tool candidates: $merge_tool_candidates"
-
-       # Loop over each candidate and stop when a valid merge tool is found.
-       for i in $merge_tool_candidates
-       do
-               init_merge_tool_path $i
-               if type "$merge_tool_path" > /dev/null 2>&1; then
-                       merge_tool=$i
-                       break
-               fi
-       done
-
-       if test -z "$merge_tool" ; then
-               echo "No known merge resolution program available."
-               exit 1
-       fi
-
-else
-       # A merge tool has been set, so verify that it's valid.
-       if ! valid_tool "$merge_tool"; then
-               echo >&2 "Unknown merge tool $merge_tool"
-               exit 1
-       fi
-
-       init_merge_tool_path "$merge_tool"
-
-       if test -z "$merge_tool_cmd" && ! type "$merge_tool_path" > /dev/null 2>&1; then
-               echo "The merge tool $merge_tool is not available as '$merge_tool_path'"
-               exit 1
-       fi
-fi
-
-
-# Launch the merge tool on each path provided by 'git diff'
-while test $# -gt 6
-do
-       launch_merge_tool "$1" "$2" "$5"
-       shift 7
-done

diff --git a/contrib/difftool/git-difftool.txt b/contrib/difftool/git-difftool.txt
deleted file mode 100644 (file)
index af68466..0000000
--- a/contrib/difftool/git-difftool.txt
+++ /dev/null
@@ -1,97 +0,0 @@
-git-difftool(1)
-===============
-
-NAME
-----
-git-difftool - Show changes using common diff tools
-
-SYNOPSIS
---------
-'git difftool' [--tool=<tool>] [-y|--no-prompt] [<'git diff' options>]
-
-DESCRIPTION
------------
-'git-difftool' is a git command that allows you to compare and edit files
-between revisions using common diff tools.  'git difftool' is a frontend
-to 'git-diff' and accepts the same options and arguments.
-
-OPTIONS
--------
--y::
---no-prompt::
-       Do not prompt before launching a diff tool.
-
--t <tool>::
---tool=<tool>::
-       Use the diff tool specified by <tool>.
-       Valid merge tools are:
-       kdiff3, kompare, tkdiff, meld, xxdiff, emerge, vimdiff, gvimdiff,
-       ecmerge, diffuse and opendiff
-+
-If a diff tool is not specified, 'git-difftool'
-will use the configuration variable `diff.tool`.  If the
-configuration variable `diff.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 `difftool.<tool>.path`. For example, you
-can configure the absolute path to kdiff3 by setting
-`difftool.kdiff3.path`. Otherwise, 'git-difftool' assumes the
-tool is available in PATH.
-+
-Instead of running one of the known diff tools,
-'git-difftool' can be customized to run an alternative program
-by specifying the command line to invoke in a configuration
-variable `difftool.<tool>.cmd`.
-+
-When 'git-difftool' is invoked with this tool (either through the
-`-t` or `--tool` option or the `diff.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`.
-
-See linkgit:git-diff[1] for the full list of supported options.
-
-CONFIG VARIABLES
-----------------
-'git-difftool' falls back to 'git-mergetool' config variables when the
-difftool equivalents have not been defined.
-
-diff.tool::
-       The default diff tool to use.
-
-difftool.<tool>.path::
-       Override the path for the given tool.  This is useful in case
-       your tool is not in the PATH.
-
-difftool.<tool>.cmd::
-       Specify the command to invoke the specified diff tool.
-+
-See the `--tool=<tool>` option above for more details.
-
-SEE ALSO
---------
-linkgit:git-diff[1]::
-        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[1]::
-        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

diff --git a/git-difftool--helper.sh b/git-difftool--helper.sh
new file mode 100755 (executable)
index 0000000..fc61416
--- /dev/null
+++ b/git-difftool--helper.sh
@@ -0,0 +1,221 @@
+#!/bin/sh
+# git-difftool--helper is a GIT_EXTERNAL_DIFF-compatible diff tool launcher.
+# This script is typically launched by using the 'git difftool'
+# convenience command.
+#
+# Copyright (c) 2009 David Aguilar
+
+# Set GIT_DIFFTOOL_NO_PROMPT to bypass the per-file prompt.
+should_prompt () {
+       test -z "$GIT_DIFFTOOL_NO_PROMPT"
+}
+
+# This function prepares temporary files and launches the appropriate
+# merge tool.
+launch_merge_tool () {
+       # Merged is the filename as it appears in the work tree
+       # Local is the contents of a/filename
+       # Remote is the contents of b/filename
+       # Custom merge tool commands might use $BASE so we provide it
+       MERGED="$1"
+       LOCAL="$2"
+       REMOTE="$3"
+       BASE="$1"
+
+       # $LOCAL and $REMOTE are temporary files so prompt
+       # the user with the real $MERGED name before launching $merge_tool.
+       if should_prompt; then
+               printf "\nViewing: '$MERGED'\n"
+               printf "Hit return to launch '%s': " "$merge_tool"
+               read ans
+       fi
+
+       # Run the appropriate merge tool command
+       case "$merge_tool" in
+       kdiff3)
+               basename=$(basename "$MERGED")
+               "$merge_tool_path" --auto \
+                       --L1 "$basename (A)" \
+                       --L2 "$basename (B)" \
+                       "$LOCAL" "$REMOTE" \
+                       > /dev/null 2>&1
+               ;;
+
+       kompare)
+               "$merge_tool_path" "$LOCAL" "$REMOTE"
+               ;;
+
+       tkdiff)
+               "$merge_tool_path" "$LOCAL" "$REMOTE"
+               ;;
+
+       meld)
+               "$merge_tool_path" "$LOCAL" "$REMOTE"
+               ;;
+
+       diffuse)
+               "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
+               ;;
+
+       vimdiff)
+               "$merge_tool_path" -d -c "wincmd l" "$LOCAL" "$REMOTE"
+               ;;
+
+       gvimdiff)
+               "$merge_tool_path" -d -c "wincmd l" -f "$LOCAL" "$REMOTE"
+               ;;
+
+       xxdiff)
+               "$merge_tool_path" \
+                       -R 'Accel.Search: "Ctrl+F"' \
+                       -R 'Accel.SearchForward: "Ctrl-G"' \
+                       "$LOCAL" "$REMOTE"
+               ;;
+
+       opendiff)
+               "$merge_tool_path" "$LOCAL" "$REMOTE" | cat
+               ;;
+
+       ecmerge)
+               "$merge_tool_path" "$LOCAL" "$REMOTE" \
+                       --default --mode=merge2 --to="$MERGED"
+               ;;
+
+       emerge)
+               "$merge_tool_path" -f emerge-files-command \
+                       "$LOCAL" "$REMOTE" "$(basename "$MERGED")"
+               ;;
+
+       *)
+               if test -n "$merge_tool_cmd"; then
+                       ( eval $merge_tool_cmd )
+               fi
+               ;;
+       esac
+}
+
+# Verifies that (difftool|mergetool).<tool>.cmd exists
+valid_custom_tool() {
+       merge_tool_cmd="$(git config difftool.$1.cmd)"
+       test -z "$merge_tool_cmd" &&
+       merge_tool_cmd="$(git config mergetool.$1.cmd)"
+       test -n "$merge_tool_cmd"
+}
+
+# Verifies that the chosen merge tool is properly setup.
+# Built-in merge tools are always valid.
+valid_tool() {
+       case "$1" in
+       kdiff3 | kompare | tkdiff | xxdiff | meld | opendiff | emerge | vimdiff | gvimdiff | ecmerge)
+               ;; # happy
+       *)
+               if ! valid_custom_tool "$1"
+               then
+                       return 1
+               fi
+               ;;
+       esac
+}
+
+# Sets up the merge_tool_path variable.
+# This handles the difftool.<tool>.path configuration.
+# This also falls back to mergetool defaults.
+init_merge_tool_path() {
+       merge_tool_path=$(git config difftool."$1".path)
+       test -z "$merge_tool_path" &&
+       merge_tool_path=$(git config mergetool."$1".path)
+       if test -z "$merge_tool_path"; then
+               case "$1" in
+               vimdiff)
+                       merge_tool_path=vim
+                       ;;
+               gvimdiff)
+                       merge_tool_path=gvim
+                       ;;
+               emerge)
+                       merge_tool_path=emacs
+                       ;;
+               *)
+                       merge_tool_path="$1"
+                       ;;
+               esac
+       fi
+}
+
+# Allow GIT_DIFF_TOOL and GIT_MERGE_TOOL to provide default values
+test -n "$GIT_MERGE_TOOL" && merge_tool="$GIT_MERGE_TOOL"
+test -n "$GIT_DIFF_TOOL" && merge_tool="$GIT_DIFF_TOOL"
+
+# If merge tool was not specified then use the diff.tool
+# configuration variable.  If that's invalid then reset merge_tool.
+# Fallback to merge.tool.
+if test -z "$merge_tool"; then
+       merge_tool=$(git config diff.tool)
+       test -z "$merge_tool" &&
+       merge_tool=$(git config merge.tool)
+       if test -n "$merge_tool" && ! valid_tool "$merge_tool"; then
+               echo >&2 "git config option diff.tool set to unknown tool: $merge_tool"
+               echo >&2 "Resetting to default..."
+               unset merge_tool
+       fi
+fi
+
+# Try to guess an appropriate merge tool if no tool has been set.
+if test -z "$merge_tool"; then
+       # We have a $DISPLAY so try some common UNIX merge tools
+       if test -n "$DISPLAY"; then
+               # If gnome then prefer meld, otherwise, prefer kdiff3 or kompare
+               if test -n "$GNOME_DESKTOP_SESSION_ID" ; then
+                       merge_tool_candidates="meld kdiff3 kompare tkdiff xxdiff gvimdiff diffuse"
+               else
+                       merge_tool_candidates="kdiff3 kompare tkdiff xxdiff meld gvimdiff diffuse"
+               fi
+       fi
+       if echo "${VISUAL:-$EDITOR}" | grep 'emacs' > /dev/null 2>&1; then
+               # $EDITOR is emacs so add emerge as a candidate
+               merge_tool_candidates="$merge_tool_candidates emerge opendiff vimdiff"
+       elif echo "${VISUAL:-$EDITOR}" | grep 'vim' > /dev/null 2>&1; then
+               # $EDITOR is vim so add vimdiff as a candidate
+               merge_tool_candidates="$merge_tool_candidates vimdiff opendiff emerge"
+       else
+               merge_tool_candidates="$merge_tool_candidates opendiff emerge vimdiff"
+       fi
+       echo "merge tool candidates: $merge_tool_candidates"
+
+       # Loop over each candidate and stop when a valid merge tool is found.
+       for i in $merge_tool_candidates
+       do
+               init_merge_tool_path $i
+               if type "$merge_tool_path" > /dev/null 2>&1; then
+                       merge_tool=$i
+                       break
+               fi
+       done
+
+       if test -z "$merge_tool" ; then
+               echo "No known merge resolution program available."
+               exit 1
+       fi
+
+else
+       # A merge tool has been set, so verify that it's valid.
+       if ! valid_tool "$merge_tool"; then
+               echo >&2 "Unknown merge tool $merge_tool"
+               exit 1
+       fi
+
+       init_merge_tool_path "$merge_tool"
+
+       if test -z "$merge_tool_cmd" && ! type "$merge_tool_path" > /dev/null 2>&1; then
+               echo "The merge tool $merge_tool is not available as '$merge_tool_path'"
+               exit 1
+       fi
+fi
+
+
+# Launch the merge tool on each path provided by 'git diff'
+while test $# -gt 6
+do
+       launch_merge_tool "$1" "$2" "$5"
+       shift 7
+done

diff --git a/git-difftool.perl b/git-difftool.perl
new file mode 100755 (executable)
index 0000000..8857ac8
--- /dev/null
+++ b/git-difftool.perl
@@ -0,0 +1,76 @@
+#!/usr/bin/env perl
+# Copyright (c) 2009 David Aguilar
+#
+# This is a wrapper around the GIT_EXTERNAL_DIFF-compatible
+# git-difftool--helper script.  This script exports
+# GIT_EXTERNAL_DIFF and GIT_PAGER for use by git, and
+# GIT_DIFFTOOL_NO_PROMPT and GIT_DIFF_TOOL for use by git-difftool--helper.
+# Any arguments that are unknown to this script are forwarded to 'git diff'.
+
+use strict;
+use warnings;
+use Cwd qw(abs_path);
+use File::Basename qw(dirname);
+
+my $DIR = abs_path(dirname($0));
+
+
+sub usage
+{
+       print << 'USAGE';
+usage: git difftool [--tool=<tool>] [-y|--no-prompt] ["git diff" options]
+USAGE
+       exit 1;
+}
+
+sub setup_environment
+{
+       $ENV{PATH} = "$DIR:$ENV{PATH}";
+       $ENV{GIT_PAGER} = '';
+       $ENV{GIT_EXTERNAL_DIFF} = 'git-difftool--helper';
+}
+
+sub exe
+{
+       my $exe = shift;
+       if ($^O eq 'MSWin32' || $^O eq 'msys') {
+               return "$exe.exe";
+       }
+       return $exe;
+}
+
+sub generate_command
+{
+       my @command = (exe('git'), 'diff');
+       my $skip_next = 0;
+       my $idx = -1;
+       for my $arg (@ARGV) {
+               $idx++;
+               if ($skip_next) {
+                       $skip_next = 0;
+                       next;
+               }
+               if ($arg eq '-t' || $arg eq '--tool') {
+                       usage() if $#ARGV <= $idx;
+                       $ENV{GIT_DIFF_TOOL} = $ARGV[$idx + 1];
+                       $skip_next = 1;
+                       next;
+               }
+               if ($arg =~ /^--tool=/) {
+                       $ENV{GIT_DIFF_TOOL} = substr($arg, 7);
+                       next;
+               }
+               if ($arg eq '-y' || $arg eq '--no-prompt') {
+                       $ENV{GIT_DIFFTOOL_NO_PROMPT} = 'true';
+                       next;
+               }
+               if ($arg eq '-h' || $arg eq '--help') {
+                       usage();
+               }
+               push @command, $arg;
+       }
+       return @command
+}
+
+setup_environment();
+exec(generate_command());