mergetool: dissect strings with shell variable magic instead of `expr`

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. There are
also some that can be replaced with shell builtins. Do so with `expr`.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-mergetool.sh b/git-mergetool.sh
index 88fa6a914a172877991ae9890cae1a42ca51fb89..8a937f680faef205fb466577b4120e7a3e9b4078 100755 (executable)
--- 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 ;;