Merge branch 'ph/stash-rerere'

"git stash" internally used "git merge-recursive" backend, which did
not trigger "rerere" upon conflicts unlike other mergy operations.

* ph/stash-rerere:
  stash: invoke rerere in case of conflict
  test: git-stash conflict sets up rerere

git-stash.sh

@@ -469,6 +469,7 @@ apply_stash () {
 	else
 		# Merge conflict; keep the exit status from merge-recursive
 		status=$?
+		git rerere
 		if test -n "$INDEX_OPTION"
 		then
 			gettextln "Index was not unstashed." >&2

t/t7610-mergetool.sh

@@ -55,6 +55,16 @@ test_expect_success 'setup' '
     git rm file12 &&
     git commit -m "branch1 changes" &&
 
+    git checkout -b stash1 master &&
+    echo stash1 change file11 >file11 &&
+    git add file11 &&
+    git commit -m "stash1 changes" &&
+
+    git checkout -b stash2 master &&
+    echo stash2 change file11 >file11 &&
+    git add file11 &&
+    git commit -m "stash2 changes" &&
+
     git checkout master &&
     git submodule update -N &&
     echo master updated >file1 &&
@@ -193,7 +203,35 @@ test_expect_success 'mergetool skips resolved paths when rerere is active' '
     git reset --hard
 '
 
+test_expect_success 'conflicted stash sets up rerere'  '
+    git config rerere.enabled true &&
+    git checkout stash1 &&
+    echo "Conflicting stash content" >file11 &&
+    git stash &&
+
+    git checkout --detach stash2 &&
+    test_must_fail git stash apply &&
+
+    test -n "$(git ls-files -u)" &&
+    conflicts="$(git rerere remaining)" &&
+    test "$conflicts" = "file11" &&
+    output="$(git mergetool --no-prompt)" &&
+    test "$output" != "No files need merging" &&
+
+    git commit -am "save the stash resolution" &&
+
+    git reset --hard stash2 &&
+    test_must_fail git stash apply &&
+
+    test -n "$(git ls-files -u)" &&
+    conflicts="$(git rerere remaining)" &&
+    test -z "$conflicts" &&
+    output="$(git mergetool --no-prompt)" &&
+    test "$output" = "No files need merging"
+'
+
 test_expect_success 'mergetool takes partial path' '
+    git reset --hard
     git config rerere.enabled false &&
     git checkout -b test12 branch1 &&
     git submodule update -N &&