rerere: handle leftover rr-cache/$ID directory and postimage files

If by some accident there is only $GIT_DIR/rr-cache/$ID directory
existed, we wouldn't have recorded a preimage for a conflict that
is newly encountered, which would mean after a manual resolution,
we wouldn't have recorded it by storing the postimage, because the
logic used to be "if there is no rr-cache/$ID directory, then we are
the first so record the preimage".  Instead, record preimage if we
do not have one.

In addition, if there is only $GIT_DIR/rr-cache/$ID/postimage
without corresponding preimage, we would have tried to call into
merge() and punted.

These would have been a situation frustratingly hard to recover
from.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/rerere.c b/rerere.c
index fbdade87209a7e313488d52d7b8295281c81d769..a1e296312ba25ee08e892b02460552e90b9a553e 100644 (file)
--- a/rerere.c
+++ b/rerere.c
@@ -117,7 +117,9 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
 
 static int has_rerere_resolution(const struct rerere_id *id)
 {
-       return (id->collection->status & RR_HAS_POSTIMAGE);
+       const int both = RR_HAS_POSTIMAGE|RR_HAS_PREIMAGE;
+
+       return ((id->collection->status & both) == both);
 }
 
 static struct rerere_id *new_rerere_id_hex(char *hex)
@@ -806,24 +808,30 @@ static int do_plain_rerere(struct string_list *rr, int fd)
                string_list_insert(rr, path)->util = id;
 
                /*
-                * If the directory does not exist, create
-                * it.  mkdir_in_gitdir() will fail with
-                * EEXIST if there already is one.
-                *
-                * NEEDSWORK: make sure "gc" does not remove
-                * preimage without removing the directory.
+                * Ensure that the directory exists.
+                * mkdir_in_gitdir() will fail with EEXIST if there
+                * already is one.
                 */
-               if (mkdir_in_gitdir(rerere_path(id, NULL)))
-                       continue;
+               if (mkdir_in_gitdir(rerere_path(id, NULL)) &&
+                   errno != EEXIST)
+                       continue; /* NEEDSWORK: perhaps we should die? */
 
-               /*
-                * We are the first to encounter this
-                * conflict.  Ask handle_file() to write the
-                * normalized contents to the "preimage" file.
-                */
-               handle_file(path, NULL, rerere_path(id, "preimage"));
-               id->collection->status |= RR_HAS_PREIMAGE;
-               fprintf(stderr, "Recorded preimage for '%s'\n", path);
+               if (id->collection->status & RR_HAS_PREIMAGE) {
+                       ;
+               } else {
+                       /*
+                        * We are the first to encounter this
+                        * conflict.  Ask handle_file() to write the
+                        * normalized contents to the "preimage" file.
+                        *
+                        * NEEDSWORK: what should happen if we had a
+                        * leftover postimage that is totally
+                        * unrelated?  Perhaps we should unlink it?
+                        */
+                       handle_file(path, NULL, rerere_path(id, "preimage"));
+                       id->collection->status |= RR_HAS_PREIMAGE;
+                       fprintf(stderr, "Recorded preimage for '%s'\n", path);
+               }
        }
 
        for (i = 0; i < rr->nr; i++)

diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index ed9c91e25b584c2241c238f9c6ffad9a3a327d2c..c4280110bc173ade9b2a7339f6f17938cd951e6d 100755 (executable)
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -184,12 +184,27 @@ test_expect_success 'rerere updates postimage timestamp' '
 '
 
 test_expect_success 'rerere clear' '
-       rm $rr/postimage &&
+       mv $rr/postimage .git/post-saved &&
        echo "$sha1     a1" | perl -pe "y/\012/\000/" >.git/MERGE_RR &&
        git rerere clear &&
        ! test -d $rr
 '
 
+test_expect_success 'leftover directory' '
+       git reset --hard &&
+       mkdir -p $rr &&
+       test_must_fail git merge first &&
+       test -f $rr/preimage
+'
+
+test_expect_success 'missing preimage' '
+       git reset --hard &&
+       mkdir -p $rr &&
+       cp .git/post-saved $rr/postimage &&
+       test_must_fail git merge first &&
+       test -f $rr/preimage
+'
+
 test_expect_success 'set up for garbage collection tests' '
        mkdir -p $rr &&
        echo Hello >$rr/preimage &&