[PATCH 0/3] Support stdio access to lockfiles

[Michael Haggerty <mhagger@alum.mit.edu>]

This series applies on top of the series "Lockfile correctness and
refactoring" (Junio's branch mh/lockfile).

There are already two callers that write to lockfiles using stdio. But
they currently need intimate knowledge of the lockfile implementation
to work correctly; for example, they have to call fclose() themselves
and set lk->fd to -1 to prevent the file from being closed again. This
is awkward and error-prone.

So provide official API support for stdio-based access to lockfiles.
Add a new function fdopen_lock_file(), which returns a (FILE *)
associated with an open lockfile, and teach close_lock_file() (and
therefore also commit_lock_file(), rollback_lock_file(), etc.) to use
fclose() instead of close() on lockfiles for which fdopen_lock_file()
has been called.

...except in the signal handler, where calling fclose() is not
permitted. In the signal handler call close() on any still-open
lockfiles regardless of whether they have been fdopen()ed. Since the
very next step is to delete the file, this should be OK.

The second and third patches rewrite the two callers who currently
fdopen() lockfiles to use the new function. I didn't look around for
other lockfile users that might be simplified and/or sped up by
converting them to use stdio; probably there are some.

This improvement was initially discussed when the second fdopen()
callsite was added [1] and also when discussing inconsistencies
between the documentation and real life in the context of the
mh/lockfile patch series [2].

Michael

[1] http://thread.gmane.org/gmane.comp.version-control.git/256729/focus=256734
[2] http://thread.gmane.org/gmane.comp.version-control.git/257504/focus=257553

Michael Haggerty (3):
  fdopen_lock_file(): access a lockfile using stdio
  dump_marks(): reimplement using fdopen_lock_file()
  commit_packed_refs(): reimplement using fdopen_lock_file()

 Documentation/technical/api-lockfile.txt | 34 +++++++++++++++--------
 fast-import.c                            | 21 ++-------------
 lockfile.c                               | 46 ++++++++++++++++++++++++++++----
 lockfile.h                               |  4 +++
 refs.c                                   |  5 +---
 5 files changed, 71 insertions(+), 39 deletions(-)

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2.1.0