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>

1 files changed, 221 insertions, 0 deletions

diff --git a/git-difftool--helper.sh b/git-difftool--helper.sh
new file mode 100755
index 0000000000..fc61416acb
--- /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