[PATCH 2/3] mergetool: dissect strings with shell variable magic instead of `expr`

From: Johannes Sixt <j6t@kdbg.org>
Date: Jun 10, 2019, 08:58 UTC
Message-ID: <2a33ca20af41d68a5bb4e2cf1e5ae32fddf2796c.1560152205.git.j6t@kdbg.org>
In-Reply-To: <cover.1560152205.git.j6t@kdbg.org>

git-mergetool spawns an enormous amount of processes. For this reason, the test script, t7610, is exceptionally slow, in particular, on Windows. Most of the processes are invocations of git, but there are also some that can be replaced with shell builtins. Do so with `expr`.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
---
 git-mergetool.sh | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/git-mergetool.sh b/git-mergetool.sh
index 88fa6a914a..8a937f680f 100755
--- a/git-mergetool.sh
+++ b/git-mergetool.sh
@@ -228,9 +228,8 @@ stage_submodule () {
 }
 
 checkout_staged_file () {
-	tmpfile=$(expr \
-		"$(git checkout-index --temp --stage="$1" "$2" 2>/dev/null)" \
-		: '\([^	]*\)	')
+	tmpfile="$(git checkout-index --temp --stage="$1" "$2" 2>/dev/null)" &&
+	tmpfile=${tmpfile%%'	'*}
 
 	if test $? -eq 0 && test -n "$tmpfile"
 	then
@@ -255,13 +254,16 @@ merge_file () {
 		return 1
 	fi
 
-	if BASE=$(expr "$MERGED" : '\(.*\)\.[^/]*$')
-	then
-		ext=$(expr "$MERGED" : '.*\(\.[^/]*\)$')
-	else
+	# extract file extension from the last path component
+	case "${MERGED##*/}" in
+	*.*)
+		ext=.${MERGED##*.}
+		BASE=${MERGED%"$ext"}
+		;;
+	*)
 		BASE=$MERGED
 		ext=
-	fi
+	esac
 
 	mergetool_tmpdir_init
 
@@ -406,7 +408,7 @@ main () {
 		-t|--tool*)
 			case "$#,$1" in
 			*,*=*)
-				merge_tool=$(expr "z$1" : 'z-[^=]*=\(.*\)')
+				merge_tool=${1#*=}
 				;;
 			1,*)
 				usage ;;

-- 
2.21.0.285.gc38d92e052