mergetool: Skip autoresolved paths

When mergetool is run without path limiters it loops
over each entry in 'git ls-files -u'.  This includes
autoresolved paths.

Teach mergetool to only merge files listed in 'rerere status'
when rerere is enabled.

There are some subtle but harmless changes in behavior.
We now call cd_to_toplevel when no paths are given.
We do this because 'rerere status' paths are always relative
to the root.  This is beneficial for the non-rerere use as
well in that mergetool now runs against all unmerged files
regardless of the current directory.

This also slightly tweaks the output when run without paths
to be more readable.

The old output:

Merging the files: foo
bar
baz

The new output:

Merging:
foo
bar
baz

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

git-mergetool.sh

@@ -264,17 +264,35 @@ merge_keep_temporaries="$(git config --bool mergetool.keepTemporaries || echo fa
 
 last_status=0
 rollup_status=0
+rerere=false
+
+files_to_merge() {
+    if test "$rerere" = true
+    then
+	git rerere status
+    else
+	git ls-files -u | sed -e 's/^[^	]*	//' | sort -u
+    fi
+}
+
 
 if test $# -eq 0 ; then
-    files=$(git ls-files -u | sed -e 's/^[^	]*	//' | sort -u)
+    cd_to_toplevel
+
+    if test -e "$GIT_DIR/MERGE_RR"
+    then
+	rerere=true
+    fi
+
+    files=$(files_to_merge)
     if test -z "$files" ; then
 	echo "No files need merging"
 	exit 0
     fi
-    echo Merging the files: "$files"
-    git ls-files -u |
-    sed -e 's/^[^	]*	//' |
-    sort -u |
+    printf "Merging:\n"
+    printf "$files\n"
+
+    files_to_merge |
     while IFS= read i
     do
 	if test $last_status -ne 0; then

t/t7610-mergetool.sh

@@ -14,6 +14,7 @@ Testing basic merge tool invocation'
 # running mergetool
 
 test_expect_success 'setup' '
+    git config rerere.enabled true &&
     echo master >file1 &&
     mkdir subdir &&
     echo master sub >subdir/file3 &&
@@ -71,19 +72,40 @@ test_expect_success 'mergetool in subdir' '
     cd subdir && (
     test_must_fail git merge master >/dev/null 2>&1 &&
     ( yes "" | git mergetool file3 >/dev/null 2>&1 ) &&
-    test "$(cat file3)" = "master new sub" )
+    test "$(cat file3)" = "master new sub") &&
+    cd ..
 '
 
-# We can't merge files from parent directories when running mergetool
-# from a subdir. Is this a bug?
-#
-#test_expect_failure 'mergetool in subdir' '
-#    cd subdir && (
-#    ( yes "" | git mergetool ../file1 >/dev/null 2>&1 ) &&
-#    ( yes "" | git mergetool ../file2 >/dev/null 2>&1 ) &&
-#    test "$(cat ../file1)" = "master updated" &&
-#    test "$(cat ../file2)" = "master new" &&
-#    git commit -m "branch1 resolved with mergetool - subdir" )
-#'
+test_expect_success 'mergetool on file in parent dir' '
+    cd subdir && (
+    ( yes "" | git mergetool ../file1 >/dev/null 2>&1 ) &&
+    ( yes "" | git mergetool ../file2 >/dev/null 2>&1 ) &&
+    test "$(cat ../file1)" = "master updated" &&
+    test "$(cat ../file2)" = "master new" &&
+    git commit -m "branch1 resolved with mergetool - subdir") &&
+    cd ..
+'
+
+test_expect_success 'mergetool skips autoresolved' '
+    git checkout -b test4 branch1 &&
+    test_must_fail git merge master &&
+    test -n "$(git ls-files -u)" &&
+    output="$(git mergetool --no-prompt)" &&
+    test "$output" = "No files need merging" &&
+    git reset --hard
+'
+
+test_expect_success 'mergetool merges all from subdir' '
+    cd subdir && (
+    git config rerere.enabled false &&
+    test_must_fail git merge master &&
+    git mergetool --no-prompt &&
+    test "$(cat ../file1)" = "master updated" &&
+    test "$(cat ../file2)" = "master new" &&
+    test "$(cat file3)" = "master new sub" &&
+    git add ../file1 ../file2 file3 &&
+    git commit -m "branch2 resolved by mergetool from subdir") &&
+    cd ..
+'
 
 test_done