Hi,
Michael Haggerty wrote:
> 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@xxxxxxxxxxxx>
Reported-by: Dave Walker <dawalker@xxxxxxxxxx>
[...]
> refs/packed-backend.c | 24 ++++++++++++++++++------
> t/t3210-pack-refs.sh | 15 +++++++++++++++
> 2 files changed, 33 insertions(+), 6 deletions(-)
The patch looks good, except for one nit marked below (*). I'll apply
it locally and ask people to test it, probably tomorrow morning.
Reviewed-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
Thanks for writing it. Patch left unsnipped for reference.
> diff --git a/refs/packed-backend.c b/refs/packed-backend.c
> index a28befbfa3..59e7d1a509 100644
> --- 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 2bb4b25ed9..0d8a03e2a9 100755
> --- 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 'pack symlinked packed-refs' '
(*) Does this need a SYMLINKS prereq to avoid trouble on Windows?
> + # 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
