[PATCH 0/7] Make "$remote/$branch" work with unconventional refspecs

The "$remote/$branch" syntax can be interpreted in two subtly different ways:

 1. A shorthand name for the remote-tracking branch corresponding to a
    specific $branch from a specific $remote.

 2. A refname fragment, which - when appended to "refs/remotes/" -
    yields the remote-tracking branch corresponding to a specific
    $branch from a specific $remote.

For the current default/conventional refspecs, both interpretations are true and equally valid. However, when configuring non-default refspecs (such as the +refs/heads/*:refs/remotes/origin/heads/*), it becomes obvious that the current code follows the latter interpretation: The "$remote/$branch" shorthand will no longer work, and you are forced to use "$remote/heads/$branch" instead.

I argue that the former interpretation is what most users intuitively expect, and that we should work towards making Git follow the same interpretation:

Instead of prepending "refs/remotes/" to convert "$remote/$branch" into a full refname, we should find "$remote" in the repo config, and then map "refs/heads/$branch" through $remote's fetch refspec(s), to find the remote-tracking branch that properly corresponds to the specific $branch in the $remote repo.

This goal is achieved by the final patch in this series, and most of the preceding patches serve as preliminary changes and refactoring to support this.

Patch #1 is the exception in that it is a self-contained bugfix for a scanf-related problem I ran across while working on the patch series.

Patches #2 and #3 introduce a new test intended to verify Git's usability when working with remote ref namespaces (which rely on setting up unconventional refspecs). For now, this test is fairly thin, but it should be expanded as we find more problems with these kinds of setups.

Patches #4 and #5 are pure refactorings to reorganize the code that expands shorthand names to full refnames and vice versa. The idea is to associate the patterns that are used to expand/shorten ref names with the actual function that does the expansion/shortening, so that we can later add patterns that uses different expand/shorten functions.

Patch #6 teaches Git to realize when - in the context of communication with a remote repo - it's expanding shorthand refs into either local refnames, or remote refnames. It is important that any expansion rules relying on local repo configuration are not allowed to expand shorthand names on behalf of the remote repo.

Finally, patch #7 introduces a new rule and associated expand/shorten functions mapping "$remote/$branch"-type shorthand names to/from their remote-tracking branch counterparts, by using the configured refspecs as described above. This rule is obviously only applied to local refs, as it would be wrong for a repo to use its local config to dictate a ref expansion in a remote repo.

The series has been build on recent 'next', and although it also applies cleanly to v1.8.3-rc1, it will cause a test failure in t7900, since it depends on the jh/checkout-auto-tracking topic, which is currently cooking.

Have fun! :)

...Johan

Johan Herland (7):
  shorten_unambiguous_ref(): Allow shortening refs/remotes/origin/HEAD to origin
  t7900: Start testing usability of namespaced remote refs
  t7900: Demonstrate failure to expand "$remote/$branch" according to refspecs
  refs.c: Refactor rules for expanding shorthand names into full refnames
  refs.c: Refactor code for shortening full refnames into shorthand names
  refname_match(): Caller must declare if we're matching local or remote refs
  refs.c: Add rules for resolving refs using remote refspecs

 cache.h                                        |   4 -
 refs.c                                         | 260 +++++++++++++++++--------
 refs.h                                         |  14 ++
 remote.c                                       |  15 +-
 t/t6300-for-each-ref.sh                        |  12 ++
 t/t7900-working-with-namespaced-remote-refs.sh | 133 +++++++++++++
 6 files changed, 342 insertions(+), 96 deletions(-)
 create mode 100755 t/t7900-working-with-namespaced-remote-refs.sh