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contrib/difftool: use a separate config namespace for difftool commands

Some users have different mergetool and difftool settings, so teach
difftool to read config vars from the difftool.* namespace.  This allows
having distinct configurations for the diff and merge scenarios.

We don't want to force existing users to set new values for no reason
so difftool falls back to existing mergetool config variables when the
difftool equivalents are not defined.

Signed-off-by: David Aguilar <>
Signed-off-by: Junio C Hamano <>
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1 parent f4e52f0 commit 2464456a6ac9216d59d9e2cf0d86fee072f63cf8 @davvid davvid committed with gitster Mar 9, 2009
Showing with 32 additions and 23 deletions.
  1. +3 −3 contrib/difftool/git-difftool
  2. +14 −5 contrib/difftool/git-difftool-helper
  3. +15 −15 contrib/difftool/git-difftool.txt
@@ -4,7 +4,7 @@
# 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_MERGE_TOOL for use by git-difftool-helper.
+# 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;
@@ -49,12 +49,12 @@ sub generate_command
if ($arg eq '-t' or $arg eq '--tool') {
usage() if $#ARGV <= $idx;
- $ENV{GIT_MERGE_TOOL} = $ARGV[$idx + 1];
+ $ENV{GIT_DIFF_TOOL} = $ARGV[$idx + 1];
$skip_next = 1;
if ($arg =~ /^--tool=/) {
- $ENV{GIT_MERGE_TOOL} = substr($arg, 7);
+ $ENV{GIT_DIFF_TOOL} = substr($arg, 7);
if ($arg eq '--no-prompt') {
@@ -128,8 +128,10 @@ launch_merge_tool () {
-# Verifies that mergetool.<tool>.cmd exists
+# Verifies that (difftool|mergetool).<tool>.cmd exists
valid_custom_tool() {
+ merge_tool_cmd="$(git config difftool.$1.cmd)"
+ test -z "$merge_tool_cmd" &&
merge_tool_cmd="$(git config mergetool.$1.cmd)"
test -n "$merge_tool_cmd"
@@ -150,8 +152,11 @@ valid_tool() {
# Sets up the merge_tool_path variable.
-# This handles the mergetool.<tool>.path configuration.
+# 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 "$1" in
@@ -165,15 +170,19 @@ init_merge_tool_path() {
-# Allow the GIT_MERGE_TOOL variable to provide a default value
+# Allow GIT_DIFF_TOOL and GIT_MERGE_TOOL to provide default values
test -n "$GIT_MERGE_TOOL" && merge_tool="$GIT_MERGE_TOOL"
+test -n "$GIT_DIFF_TOOL" && merge_tool="$GIT_DIFF_TOOL"
-# If not merge tool was specified then use the merge.tool
+# If merge tool was not specified then use the diff.tool
# configuration variable. If that's invalid then reset merge_tool.
+# Fallback to merge.tool.
if test -z "$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 merge.tool set to unknown tool: $merge_tool"
+ echo >&2 "git config option diff.tool set to unknown tool: $merge_tool"
echo >&2 "Resetting to default..."
unset merge_tool
@@ -32,23 +32,23 @@ OPTIONS
vimdiff, gvimdiff, ecmerge, and opendiff
If a merge resolution program is not specified, 'git-difftool'
-will use the configuration variable `merge.tool`. If the
-configuration variable `merge.tool` is not set, 'git difftool'
+will use the configuration variable `diff.tool`. If the
+configuration variable `diff.tool` is not set, 'git-difftool'
will pick a suitable default.
You can explicitly provide a full path to the tool by setting the
-configuration variable `mergetool.<tool>.path`. For example, you
+configuration variable `difftool.<tool>.path`. For example, you
can configure the absolute path to kdiff3 by setting
-`mergetool.kdiff3.path`. Otherwise, 'git-difftool' assumes the
+`difftool.kdiff3.path`. Otherwise, 'git-difftool' assumes the
tool is available in PATH.
Instead of running one of the known merge tool programs,
'git-difftool' can be customized to run an alternative program
by specifying the command line to invoke in a configuration
-variable `mergetool.<tool>.cmd`.
+variable `difftool.<tool>.cmd`.
When 'git-difftool' is invoked with this tool (either through the
-`-t` or `--tool` option or the `merge.tool` configuration variable)
+`-t` or `--tool` option or the `diff.tool` configuration variable)
the configured command line will be invoked with the following
variables available: `$LOCAL` is set to the name of the temporary
file containing the contents of the diff pre-image and `$REMOTE`
@@ -61,24 +61,24 @@ with custom merge tool commands and has the same value as `$LOCAL`.
- The default merge tool to use.
-See the `--tool=<tool>` option above for more details.
+'git-difftool' falls back to 'git-mergetool' config variables when the
+difftool equivalents have not been defined.
- The original, unedited file content can be saved to a file with
- a `.orig` extension. Defaults to `true` (i.e. keep the backup files).
+ The default merge tool to use.
Override the path for the given tool. This is useful in case
your tool is not in the PATH.
Specify the command to invoke the specified merge tool.
See the `--tool=<tool>` option above for more details.
+ The original, unedited file content can be saved to a file with
+ a `.orig` extension. Defaults to `true` (i.e. keep the backup files).

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