packed_ref_store: handle a packed-refs file that is a symlink

One of the tricks that `contrib/workdir/git-new-workdir` plays is to
making `packed-refs` in the new workdir a symlink to the `packed-refs`
file in the original repository. Before
42dfa7ecef ("commit_packed_refs(): use a staging file separate from
the lockfile", 2017-06-23), a lockfile was used as the staging file,
and because the `LOCK_NO_DEREF` was not used, the pointed-to file was
locked and modified.

But after that commit, the staging file was created using a tempfile,
with the end result that rewriting the `packed-refs` file in the
workdir overwrote the symlink rather than the original `packed-refs`
file.

Change `commit_packed_refs()` to use `get_locked_file_path()` to find
the path of the file that it should overwrite. Since that path was
properly resolved when the lockfile was created, this restores the
pre-42dfa7ecef behavior.

Also add a test case to document this use case and prevent a
regression like this from recurring.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index a28befbfa3198fcaebf73f6d835943efc316c6aa..59e7d1a5097b51f2358e4970a5253c20c02abe82 100644 (file)
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -610,19 +610,27 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
        struct packed_ref_cache *packed_ref_cache =
                get_packed_ref_cache(refs);
        int ok;
+       int ret = -1;
        struct strbuf sb = STRBUF_INIT;
        FILE *out;
        struct ref_iterator *iter;
+       char *packed_refs_path;
 
        if (!is_lock_file_locked(&refs->lock))
                die("BUG: commit_packed_refs() called when unlocked");
 
-       strbuf_addf(&sb, "%s.new", refs->path);
+       /*
+        * If packed-refs is a symlink, we want to overwrite the
+        * symlinked-to file, not the symlink itself. Also, put the
+        * staging file next to it:
+        */
+       packed_refs_path = get_locked_file_path(&refs->lock);
+       strbuf_addf(&sb, "%s.new", packed_refs_path);
        if (create_tempfile(&refs->tempfile, sb.buf) < 0) {
                strbuf_addf(err, "unable to create file %s: %s",
                            sb.buf, strerror(errno));
                strbuf_release(&sb);
-               return -1;
+               goto out;
        }
        strbuf_release(&sb);
 
@@ -660,17 +668,21 @@ int commit_packed_refs(struct ref_store *ref_store, struct strbuf *err)
                goto error;
        }
 
-       if (rename_tempfile(&refs->tempfile, refs->path)) {
+       if (rename_tempfile(&refs->tempfile, packed_refs_path)) {
                strbuf_addf(err, "error replacing %s: %s",
                            refs->path, strerror(errno));
-               return -1;
+               goto out;
        }
 
-       return 0;
+       ret = 0;
+       goto out;
 
 error:
        delete_tempfile(&refs->tempfile);
-       return -1;
+
+out:
+       free(packed_refs_path);
+       return ret;
 }
 
 /*

diff --git a/t/t3210-pack-refs.sh b/t/t3210-pack-refs.sh
index 2bb4b25ed9f1d3807a5180be447440e1be310e97..afa27ffe2d869a5e7fdf8318d5b9957208a96c52 100755 (executable)
--- a/t/t3210-pack-refs.sh
+++ b/t/t3210-pack-refs.sh
@@ -238,4 +238,19 @@ test_expect_success 'retry acquiring packed-refs.lock' '
        git -c core.packedrefstimeout=3000 pack-refs --all --prune
 '
 
+test_expect_success SYMLINKS 'pack symlinked packed-refs' '
+       # First make sure that symlinking works when reading:
+       git update-ref refs/heads/loosy refs/heads/master &&
+       git for-each-ref >all-refs-before &&
+       mv .git/packed-refs .git/my-deviant-packed-refs &&
+       ln -s my-deviant-packed-refs .git/packed-refs &&
+       git for-each-ref >all-refs-linked &&
+       test_cmp all-refs-before all-refs-linked &&
+       git pack-refs --all --prune &&
+       git for-each-ref >all-refs-packed &&
+       test_cmp all-refs-before all-refs-packed &&
+       test -h .git/packed-refs &&
+       test "$(readlink .git/packed-refs)" = "my-deviant-packed-refs"
+'
+
 test_done