am --skip/--abort: merge HEAD/ORIG_HEAD tree into index

After running "git am --abort", and then running "git reset --hard",
files that were not modified would still be re-checked out.

This is because clean_index() in builtin/am.c mistakenly called the
read_tree() function, which overwrites all entries in the index,
including the stat info.

"git am --skip" did not seem to have this issue because am_skip() called
am_run(), which called refresh_cache() to update the stat info. However,
there's still a performance penalty as the lack of stat info meant that
refresh_cache() would have to scan all files for changes.

Fix this by using unpack_trees() instead to merge the tree into the
index, so that the stat info from the index is kept.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Paul Tan <pyokagan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/am.c b/builtin/am.c
index 1399c8dd880f86190534b9c9e0a5e84f48ebeceb..3e7e66f82d2598bc4c4a540581b12c1c4a2ff5a1 100644 (file)
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1939,16 +1939,49 @@ static int fast_forward_to(struct tree *head, struct tree *remote, int reset)
        return 0;
 }
 
+/**
+ * Merges a tree into the index. The index's stat info will take precedence
+ * over the merged tree's. Returns 0 on success, -1 on failure.
+ */
+static int merge_tree(struct tree *tree)
+{
+       struct lock_file *lock_file;
+       struct unpack_trees_options opts;
+       struct tree_desc t[1];
+
+       if (parse_tree(tree))
+               return -1;
+
+       lock_file = xcalloc(1, sizeof(struct lock_file));
+       hold_locked_index(lock_file, 1);
+
+       memset(&opts, 0, sizeof(opts));
+       opts.head_idx = 1;
+       opts.src_index = &the_index;
+       opts.dst_index = &the_index;
+       opts.merge = 1;
+       opts.fn = oneway_merge;
+       init_tree_desc(&t[0], tree->buffer, tree->size);
+
+       if (unpack_trees(1, t, &opts)) {
+               rollback_lock_file(lock_file);
+               return -1;
+       }
+
+       if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
+               die(_("unable to write new index file"));
+
+       return 0;
+}
+
 /**
  * Clean the index without touching entries that are not modified between
  * `head` and `remote`.
  */
 static int clean_index(const unsigned char *head, const unsigned char *remote)
 {
-       struct lock_file *lock_file;
        struct tree *head_tree, *remote_tree, *index_tree;
        unsigned char index[GIT_SHA1_RAWSZ];
-       struct pathspec pathspec;
 
        head_tree = parse_tree_indirect(head);
        if (!head_tree)
@@ -1973,18 +2006,8 @@ static int clean_index(const unsigned char *head, const unsigned char *remote)
        if (fast_forward_to(index_tree, remote_tree, 0))
                return -1;
 
-       memset(&pathspec, 0, sizeof(pathspec));
-
-       lock_file = xcalloc(1, sizeof(struct lock_file));
-       hold_locked_index(lock_file, 1);
-
-       if (read_tree(remote_tree, 0, &pathspec)) {
-               rollback_lock_file(lock_file);
+       if (merge_tree(remote_tree))
                return -1;
-       }
-
-       if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
-               die(_("unable to write new index file"));
 
        remove_branch_state();
 

diff --git a/t/t4151-am-abort.sh b/t/t4151-am-abort.sh
index 05bdc3ee49408ac1ab35fe54d0b3bfbe401bf7cf..ea5ace99a14f7f31b63dfd9cf25123725a525519 100755 (executable)
--- a/t/t4151-am-abort.sh
+++ b/t/t4151-am-abort.sh
@@ -168,4 +168,28 @@ test_expect_success 'am --abort on unborn branch will keep local commits intact'
        test_cmp expect actual
 '
 
+test_expect_success 'am --skip leaves index stat info alone' '
+       git checkout -f --orphan skip-stat-info &&
+       git reset &&
+       test_commit skip-should-be-untouched &&
+       test-chmtime =0 skip-should-be-untouched.t &&
+       git update-index --refresh &&
+       git diff-files --exit-code --quiet &&
+       test_must_fail git am 0001-*.patch &&
+       git am --skip &&
+       git diff-files --exit-code --quiet
+'
+
+test_expect_success 'am --abort leaves index stat info alone' '
+       git checkout -f --orphan abort-stat-info &&
+       git reset &&
+       test_commit abort-should-be-untouched &&
+       test-chmtime =0 abort-should-be-untouched.t &&
+       git update-index --refresh &&
+       git diff-files --exit-code --quiet &&
+       test_must_fail git am 0001-*.patch &&
+       git am --abort &&
+       git diff-files --exit-code --quiet
+'
+
 test_done