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Thomas Rast
ad0e623332 test-lib: support running tests under valgrind in parallel
With the new --valgrind-parallel=<n> option, we support running the
tests in a single test script under valgrind in parallel using 'n'
processes.

This really follows the dumbest approach possible, as follows:

* We spawn the test script 'n' times, using a throw-away
  TEST_OUTPUT_DIRECTORY.  Each of the instances is given options that
  ensures that it only runs every n-th test under valgrind, but
  together they cover the entire range.

* We add up the numbers from the individual tests, and provide the
  usual output.

This is really a gross hack at this point, and should be improved.  In
particular we should keep the actual outputs somewhere more easily
discoverable, and summarize them to the user.

Nevertheless, this is already workable and gives a speedup of more
than 2 on a dual-core (hyperthreaded) machine, using n=4.  This is
expected since the overhead of valgrind is so big (on the order of 20x
under good conditions, and a large startup overhead at every git
invocation) that redundantly running the non-valgrind tests in between
is not that expensive.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 12:24:06 -07:00
Thomas Rast
e939e15d24 test-lib: allow prefixing a custom string before "ok N" etc.
This is not really meant for external use, and thus not documented. It
allows the next commit to neatly distinguish between sub-tests and the
main run.

The format is intentionally not valid TAP.  The use in the next commit
would not result in anything valid either way, and it seems better to
make it obvious.

Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 12:24:06 -07:00
Thomas Rast
5dfc368f5e test-lib: valgrind for only tests matching a pattern
With the new --valgrind-only=<pattern> option, one can enable
--valgrind at a per-test granularity, exactly analogous to
--verbose-only from the previous commit.

The options are wired such that --valgrind implies --verbose (as
before), but --valgrind-only=<pattern> implies
--verbose-only=<pattern> unless --verbose is also in effect.

Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 12:24:06 -07:00
Thomas Rast
ff09af3fb8 test-lib: verbose mode for only tests matching a pattern
With the new --verbose-only=<pattern> option, one can enable --verbose
at a per-test granularity.  The pattern is matched against the test
number, e.g.

  ./t0000-basic.sh --verbose-only='2[0-2]'

to see only the full output of test 20-22, while showing the rest in the
one-liner format.

As suggested by Jeff King, this takes care to wrap the entire
test_expect_* block, but nothing else, in the verbose toggling.  We
can use the test_start/end functions from the previous commit for the
purpose.

This is arguably not *too* useful on its own, but makes the next patch
easier to follow.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 12:24:06 -07:00
Thomas Rast
517cd55fd5 test-lib: self-test that --verbose works
t0000 contains some light self-tests of test-lib.sh, but --verbose was
not covered.  Add a test.

The only catch is that the presence of a test harness influences the
output (specifically, the presence of some empty lines).  So we need
to unset TEST_HARNESS or set it to a known value.  Leaving it unset
leads to spurious test failures in the final summary, which come from
the subtest.  So we always set it.

Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 12:24:05 -07:00
W. Trevor King
4b9ced278c user-manual: Update download size for Git and the kernel
They've grown since d19fbc3 (Documentation: add git user's manual,
2007-01-07) when the stats were initially added.  I've rounded
download sizes up to the nearest multiple of ten MiB to decrease the
precision and give a bit of growing room.  Exact sizes:

  $ git clone git://git.kernel.org/pub/scm/git/git.git
  Initialized empty Git repository in /tmp/git/.git/
  remote: Counting objects: 156872, done.
  remote: Compressing objects: 100% (40826/40826), done.
  remote: Total 156872 (delta 115322), reused 155492 (delta 114094)
  Receiving objects: 100% (156872/156872), 37.29 MiB | 7.54 MiB/s, done.
  Resolving deltas: 100% (115322/115322), done.

  $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
  Initialized empty Git repository in /tmp/linux/.git/
  remote: Counting objects: 3057404, done.
  remote: Compressing objects: 100% (474769/474769), done.
  Receiving objects: 100% (3057404/3057404), 634.33 MiB | 27.95 MiB/s, done.
  remote: Total 3057404 (delta 2570385), reused 3040910 (delta 2554408)
  Resolving deltas: 100% (2570385/2570385), done.
  Checking out files: 100% (43012/43012), done.

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:35:50 -07:00
Ramkumar Ramachandra
f0f249d186 t/t5505-remote: test multiple push/pull in remotes-file
Extend the test "migrate a remote from named file in $GIT_DIR/remotes"
to test that multiple "Push:" and "Pull:" lines in the remotes-file
works as expected.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:33:58 -07:00
Ramkumar Ramachandra
f0779aef8e ls-remote doc: don't encourage use of branches-file
One outdated example encourages the use of $GIT_DIR/branches files.
Replace it with an equivalent example using a remote.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:33:58 -07:00
Ramkumar Ramachandra
88e36141d0 ls-remote doc: rewrite <repository> paragraph
Replace the <repository> paragraph containing specific references to
$GIT_DIR/branches and "." with a generic urls-or-remotes paragraph
referencing the relevant sections in the git-fetch(1) manpage.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:33:58 -07:00
Ramkumar Ramachandra
6077d36299 ls-remote doc: fix example invocation on git.git
Under the EXAMPLES section, there is one invocation on the git.git
repository that attempts to list the refs master, pu, and rc.  The ref
rc does not exist in today's repository, so remove it.  Among other
things, this example demonstrates that the "<refs>..." argument is
simply a filter; requesting a non-existent ref is not an error.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:33:58 -07:00
Ramkumar Ramachandra
1f9a5e905e t/t5505-remote: test url-with-# in branches-file
Add one more test similar to "migrate a remote from named file in
$GIT_DIR/branches" to check that a url with a # can be used to specify
the branch name (as opposed to the constant "master").

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:33:57 -07:00
Ramkumar Ramachandra
55cfde251b remote: remove dead code in read_branches_file()
The first line of the function checks that the remote-name contains a
slash ('/'), and sets the "slash" variable accordingly.  The only caller
of read_branches_file() is remote_get_1(); the calling codepath is
guarded by valid_remote_nick(), which checks that the remote does not
contain a slash.  Therefore, the "slash" variable can never be set:
remove the dead code that assumes otherwise.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:33:57 -07:00
Ramkumar Ramachandra
fe3c1956e2 t/t5505-remote: use test_path_is_missing
Replace instances of ! test -f with test_path_is_missing.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:14:33 -07:00
Ramkumar Ramachandra
294547f564 t/t5505-remote: test push-refspec in branches-file
The test "migrate a remote from named file in $GIT_DIR/branches" reads
the branches-file, but only checks that the url and fetch-refspec are
set correctly.  Check that the push-refspec is also set correctly.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:14:15 -07:00
Ramkumar Ramachandra
9b9439afd8 t/t5505-remote: modernize style
Modernize the style of all tests throughout the file:

 - Remove spurious blank lines.

 - Indent the test body.

 - Make sure that all lines end with &&, to make it easier to spot
   breaks in the chain.

 - When executing something in a subshell, put the parenthesis on
   separate lines and indent the body.  Also make sure that the
   first statement in the subshell is a 'cd'.

 - When redirecting input or output, do not use SP between
   redirection operator and the target filename.

 - Use the <<-\EOF and <<-EOF forms of heredoc, not <<EOF, when the
   command is indented and the heredoc text itself does not have to
   have a leading tab.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-23 00:08:25 -07:00
W. Trevor King
283efb0108 Documentation: Update 'linux-2.6.git' -> 'linux.git'
The 3.x tree has been out for a while now.  The -2.6 repository name
survived the initial release [1], but kernel.org now only lists
'linux.git' (for aegl as well as torvalds) [2].

[1]: http://article.gmane.org/gmane.linux.kernel/1147422
  On 2011-05-30 01:47:57 GMT, Linus Torvalds wrote:
  > ... yes, that means that my git tree is still called
  > "linux-2.6.git" on kernel.org.
[2]: http://git.kernel.org/cgit/

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-22 23:36:48 -07:00
W. Trevor King
34a25d4c90 Documentation: Update the NFS remote examples to use the staging repo
linux-nfs.org seems to have restructured their repository layout since
8391c60 (git-remote.txt: fix example url, 2007-11-02), and Bruce's
repo is now at git://git.linux-nfs.org/projects/bfields/linux.git.
Bruce also has a more richer internal branch structure (master,
everything, for-3.1, ...), so updating the existing example to use his
current repo may be confusing.

To simplify, I've replaced the NFS repo with Greg's staging repo.
I've also updated the output of the surrounding commands to match the
output of a current run through.

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-22 23:35:17 -07:00
W. Trevor King
f22a6543d1 doc/clone: Pick more compelling paths for the --reference example
There may be times when using one of your local repositories as a
reference for a new clone make sense, but the implied version-bump in
the old example isn't one of them.  I think a more intuitive example
is multi-user system with a central reference clone, and the new paths
hint at this use case.

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-22 23:35:00 -07:00
W. Trevor King
8c8fc53c7d doc/clone: Remove the '--bare -l -s' example
There are other examples in git-clone.txt demonstrating both '--bare'
and '-l -s'.

Signed-off-by: W. Trevor King <wking@tremily.us>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-22 23:34:54 -07:00
Jeff King
5bdc47eb55 lib-httpd/apache.conf: check version only after mod_version loads
Commit 0442743 introduced an <IfVersion> directive near the
top of the apache config file. However, at that point we
have not yet checked for and loaded the mod_version module.
This means that the directive will behave oddly if
mod_version is dynamically loaded, failing to match when it
should.

We can fix this by moving the whole block below the
LoadModule directive for mod_version.

Reported-by: Brian Gernhardt <brian@gernhardtsoftware.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 13:58:06 -07:00
Junio C Hamano
3e7a5b489e Sync with maint
* maint:
  completion: complete diff --word-diff
2013-06-21 11:26:41 -07:00
Junio C Hamano
aff2e7c067 t6003: add --author-date-order test
Tweak the --topo/date-order test vector a bit and mark the author
dates of two commits (a2 and a3) earlier than their own committer
dates, making them much older than other commits that are made on
parallel branches to simulate the case where a long running topic
was rebased recently.

They will show up as recent in the --date-order output due to their
timestamps, but they appear a lot later in the --author-date-order
output, even though their committer timestamp says otherwise.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 11:16:31 -07:00
Junio C Hamano
11667316d0 topology tests: teach a helper to set author dates as well
Introduce on_dates helper that is similar to on_committer_date but
also sets the author date, not just the committer date.

At this step, just set the same timestamp to the author date as the
committer date, as no test looks at author date yet.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 11:16:31 -07:00
Junio C Hamano
b9f80fdaea t6003: add --date-order test
The "--date-order" output is a slight twist of "--topo-order" in
that commits from parallel histories are shown in their committer
date order without an attempt to clump commits from a single line
of history together like --topo-order does.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 11:16:31 -07:00
Junio C Hamano
841dc6935e topology tests: teach a helper to take abbreviated timestamps
The on_committer_date helper in t/lib-t6000 is used in t6002 and
t6003 with timestamps on a single day within a single minute
(i.e. 1971-08-16 00:00) and the tests repeat this over and over.

The actual value of the timestamp, however, does not matter very
much; only their relative ordering does.

Introduce another helper to expand only the suffix of the timestamp
to a full timestamp to make the lines shorter, and use it in this
helper.  Also, because all the commits in the test are made with
specific GIT_COMMITTER_DATE, stop unsetting it at the end of the
helper.

We'll be specifying the author timestamp to these test commits in a
later patch, which will be helped with this change.

Also remove a test that was commented-out from t6003; it used to
test a commit with the same parent listed twice, which was allowed
by mistake but was fixed long time ago.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 11:15:32 -07:00
Junio C Hamano
50e5a25222 t/lib-t6000: style fixes
Mostly fixes to initial indentation with 8-SP (they should be HT)
and wrapping long lines.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 10:16:01 -07:00
Yaakov Selkowitz
cc2f6b6865 web--browse: support /usr/bin/cygstart on Cygwin
While both GUI and console Cygwin browsers do exist, anecdotal evidence
suggests most users rely on their native Windows browser.  cygstart,
which is a long-standing part of the base Cygwin installation, will
cause the page to be opened in the default Windows browser (the one
registered to open .html files).

Signed-off-by: Yaakov Selkowitz <yselkowitz@users.sourceforge.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 09:05:15 -07:00
Jeff King
266f1fdfa9 transport-helper: be quiet on read errors from helpers
Prior to commit 81d340d4, we did not print any error message
if a remote transport helper died unexpectedly. If a helper
did not print any error message (e.g., because it crashed),
the user could be left confused. That commit tried to
rectify the situation by printing a note that the helper
exited unexpectedly.

However, this makes a much more common case worse: when a
helper does die with a useful message, we print the extra
"Reading from 'git-remote-foo failed" message. This can also
end up confusing users, as they may not even know what
remote helpers are (e.g., the fact that http support comes
through git-remote-https is purely an implementation detail
that most users do not know or care about).

Since we do not have a good way of knowing whether the
helper printed a useful error, and since the common failure
mode is for it to do so, let's default to remaining quiet.
Debuggers can dig further by setting GIT_TRANSPORT_HELPER_DEBUG.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 09:03:53 -07:00
Ramkumar Ramachandra
c0add3073a completion: complete diff --word-diff
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 08:52:16 -07:00
Thomas Rast
212eb96a96 apply: carefully strdup a possibly-NULL name
2901bbe (apply: free patch->{def,old,new}_name fields, 2012-03-21)
cleaned up the memory management of filenames in the patches, but
forgot that find_name_traditional() can return NULL as a way of saying
"I couldn't find a name".

That NULL unfortunately gets passed into xstrdup() next, resulting in
a segfault.  Use null_strdup() so as to safely propagate the null,
which will let us emit the correct error message.

Reported-by: DevHC on #git
Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-21 08:36:07 -07:00
Junio C Hamano
21ff9151e8 Update draft release notes to 1.8.4 2013-06-20 16:13:41 -07:00
Junio C Hamano
0c36f3a198 Merge branch 'cm/remote-mediawiki'
* cm/remote-mediawiki:
  git-remote-mediawiki: display message when launched directly
2013-06-20 16:02:42 -07:00
Junio C Hamano
50f6909929 Merge branch 'rs/match-trees-refactor'
Code cleanup.

* rs/match-trees-refactor:
  match-trees: factor out fill_tree_desc_strict
2013-06-20 16:02:40 -07:00
Junio C Hamano
02dfccfa40 Merge branch 'rs/logical-vs-binary-or'
Code cleanup.

* rs/logical-vs-binary-or:
  use logical OR (||) instead of binary OR (|) in logical context
2013-06-20 16:02:39 -07:00
Junio C Hamano
73018c0f0b Merge branch 'mm/color-auto-default'
Flip the default for color.ui to 'auto', which is what many
tutorials recommend new users to do.

* mm/color-auto-default:
  make color.ui default to 'auto'
  config: refactor management of color.ui's default value
2013-06-20 16:02:33 -07:00
Junio C Hamano
08bcd774f4 Merge branch 'rs/discard-index-discard-array'
* rs/discard-index-discard-array:
  read-cache: free cache in discard_index
  read-cache: add simple performance test
2013-06-20 16:02:30 -07:00
Junio C Hamano
8f0c843aab Merge branch 'nd/traces'
* nd/traces:
  git.txt: document GIT_TRACE_PACKET
  core: use env variable instead of config var to turn on logging pack access
2013-06-20 16:02:28 -07:00
Junio C Hamano
01c0615dce Merge branch 'fc/show-non-empty-errors-in-test'
* fc/show-non-empty-errors-in-test:
  test: test_must_be_empty helper
2013-06-20 16:02:24 -07:00
Junio C Hamano
0846fe1a83 Merge branch 'fc/makefile'
Makefile simplification.

* fc/makefile:
  Makefile: use $^ to avoid listing prerequisites on the command line
  build: do not install git-remote-testgit
  build: generate and clean test scripts
2013-06-20 16:02:21 -07:00
Junio C Hamano
c0266ed275 Merge branch 'js/test-ln-s-add'
Many tests that check the behaviour of symbolic links stored in the
index or the tree objects do not have to be skipped on a filesystem
that lack symbolic link support.

* js/test-ln-s-add:
  t4011: remove SYMLINKS prerequisite
  t6035: use test_ln_s_add to remove SYMLINKS prerequisite
  t3509, t4023, t4114: use test_ln_s_add to remove SYMLINKS prerequisite
  t3100: use test_ln_s_add to remove SYMLINKS prerequisite
  t3030: use test_ln_s_add to remove SYMLINKS prerequisite
  t0000: use test_ln_s_add to remove SYMLINKS prerequisite
  tests: use test_ln_s_add to remove SYMLINKS prerequisite (trivial cases)
  tests: introduce test_ln_s_add
  t3010: modernize style
  test-chmtime: Fix exit code on Windows
2013-06-20 16:02:18 -07:00
Junio C Hamano
6aeb74ec89 Merge branch 'nd/make-wildmatch-default'
* nd/make-wildmatch-default:
  Makefile: promote wildmatch to be the default fnmatch implementation
2013-06-20 16:02:14 -07:00
Thomas Rast
b4dc085a8d pull: merge into unborn by fast-forwarding from empty tree
The logic for pulling into an unborn branch was originally
designed to be used on a newly-initialized repository
(d09e79c, git-pull: allow pulling into an empty repository,
2006-11-16).  It thus did not initially deal with
uncommitted changes in the unborn branch.  The case of an
_unstaged_ untracked file was fixed by 4b3ffe5 (pull: do not
clobber untracked files on initial pull, 2011-03-25).
However, it still clobbered existing staged files, both when
the file exists in the merged commit (it will be
overwritten), and when it does not (it will be deleted).

We fix this by doing a two-way merge, where the "current"
side of the merge is an empty tree, and the "target" side is
HEAD (already updated to FETCH_HEAD at this point).  This
amounts to claiming that all work in the index was done vs.
an empty tree, and thus all content of the index is
precious.

Note that this use of read-tree just gives us protection
against overwriting index and working tree changes. It will
not actually result in a 3-way merge conflict in the index.
This is fine, as this is a rare situation, and the conflict
would not be interesting anyway (it must, by definition, be
an add/add conflict with the whole content conflicting). And
it makes it simpler for the user to recover, as they have no
HEAD to "git reset" back to.

Reported-by: Stefan Schüßler <mail@stefanschuessler.de>
Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:51:35 -07:00
Jeff King
9f48f2bd9a pull: update unborn branch tip after index
When commit d09e79c taught git to pull into an unborn
branch, it first updated the unborn branch to point at the
pulled commit, and then used read-tree to update the index
and working tree. That ordering made sense, since any
failure of the latter step would be due to filesystem
errors, and one could then recover with "git reset --hard".

Later, commit 4b3ffe5 added extra safety for existing files
in the working tree by asking read-tree to bail out when it
would overwrite such a file. This error mode is much less
"your pull failed due to random errors" and more like "we
reject this pull because it would lose data". In that case,
it makes sense not to update the HEAD ref, just as a regular
rejected merge would do.

This patch reverses the order of the update-ref and
read-tree calls, so that we do not touch the HEAD ref at all if a
merge is rejected. This also means that we would not update
HEAD in case of a transient filesystem error, but those are
presumably less rare (and one can still recover by repeating
the pull, or by accessing FETCH_HEAD directly).

While we're reorganizing the code, we can drop the "exit 1"
from the end of our command chain. We exit immediately
either way, and just calling exit without an argument will
use the exit code from the last command.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:51:25 -07:00
Michael Haggerty
5d478f5ca1 refs: do not invalidate the packed-refs cache unnecessarily
Now that we keep track of the packed-refs file metadata, we can detect
when the packed-refs file has been modified since we last read it, and
we do so automatically every time that get_packed_ref_cache() is
called.  So there is no need to invalidate the cache automatically
when lock_packed_refs() is called; usually the old copy will still be
valid.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:50:17 -07:00
Jeff King
98eeb09e8a for_each_ref: load all loose refs before packed refs
If we are iterating through the refs using for_each_ref (or
any of its sister functions), we can get into a race
condition with a simultaneous "pack-refs --prune" that looks
like this:

  0. We have a large number of loose refs, and a few packed
     refs. refs/heads/z/foo is loose, with no matching entry
     in the packed-refs file.

  1. Process A starts iterating through the refs. It loads
     the packed-refs file from disk, then starts lazily
     traversing through the loose ref directories.

  2. Process B, running "pack-refs --prune", writes out the
     new packed-refs file. It then deletes the newly packed
     refs, including refs/heads/z/foo.

  3. Meanwhile, process A has finally gotten to
     refs/heads/z (it traverses alphabetically). It
     descends, but finds nothing there.  It checks its
     cached view of the packed-refs file, but it does not
     mention anything in "refs/heads/z/" at all (it predates
     the new file written by B in step 2).

The traversal completes successfully without mentioning
refs/heads/z/foo at all (the name, of course, isn't
important; but the more refs you have and the farther down
the alphabetical list a ref is, the more likely it is to hit
the race). If refs/heads/z/foo did exist in the packed refs
file at state 0, we would see an entry for it, but it would
show whatever sha1 the ref had the last time it was packed
(which could be an arbitrarily long time ago).

This can be especially dangerous when process A is "git
prune", as it means our set of reachable tips will be
incomplete, and we may erroneously prune objects reachable
from that tip (the same thing can happen if "repack -ad" is
used, as it simply drops unreachable objects that are
packed).

This patch solves it by loading all of the loose refs for
our traversal into our in-memory cache, and then refreshing
the packed-refs cache. Because a pack-refs writer will
always put the new packed-refs file into place before
starting the prune, we know that any loose refs we fail to
see will either truly be missing, or will have already been
put in the packed-refs file by the time we refresh.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:50:17 -07:00
Jeff King
ca9199300e get_packed_ref_cache: reload packed-refs file when it changes
Once we read the packed-refs file into memory, we cache it
to save work on future ref lookups. However, our cache may
be out of date with respect to what is on disk if another
process is simultaneously packing the refs. Normally it
is acceptable for us to be a little out of date, since there
is no guarantee whether we read the file before or after the
simultaneous update. However, there is an important special
case: our packed-refs file must be up to date with respect
to any loose refs we read. Otherwise, we risk the following
race condition:

  0. There exists a loose ref refs/heads/master.

  1. Process A starts and looks up the ref "master". It
     first checks $GIT_DIR/master, which does not exist. It
     then loads (and caches) the packed-refs file to see if
     "master" exists in it, which it does not.

  2. Meanwhile, process B runs "pack-refs --all --prune". It
     creates a new packed-refs file which contains
     refs/heads/master, and removes the loose copy at
     $GIT_DIR/refs/heads/master.

  3. Process A continues its lookup, and eventually tries
     $GIT_DIR/refs/heads/master.  It sees that the loose ref
     is missing, and falls back to the packed-refs file. But
     it examines its cached version, which does not have
     refs/heads/master. After trying a few other prefixes,
     it reports master as a non-existent ref.

There are many variants (e.g., step 1 may involve process A
looking up another ref entirely, so even a fully qualified
refname can fail). One of the most interesting ones is if
"refs/heads/master" is already packed. In that case process
A will not see it as missing, but rather will report
whatever value happened to be in the packed-refs file before
process B repacked (which might be an arbitrarily old
value).

We can fix this by making sure we reload the packed-refs
file from disk after looking at any loose refs. That's
unacceptably slow, so we can check its stat()-validity as a
proxy, and read it only when it appears to have changed.

Reading the packed-refs file after performing any loose-ref
system calls is sufficient because we know the ordering of
the pack-refs process: it always makes sure the newly
written packed-refs file is installed into place before
pruning any loose refs. As long as those operations by B
appear in their executed order to process A, by the time A
sees the missing loose ref, the new packed-refs file must be
in place.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:50:17 -07:00
Michael Haggerty
3861253224 add a stat_validity struct
It can sometimes be useful to know whether a path in the
filesystem has been updated without going to the work of
opening and re-reading its content. We trust the stat()
information on disk already to handle index updates, and we
can use the same trick here.

This patch introduces a "stat_validity" struct which
encapsulates the concept of checking the stat-freshness of a
file. It is implemented on top of "struct stat_data" to
reuse the logic about which stat entries to trust for a
particular platform, but hides the complexity behind two
simple functions: check and update.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:50:17 -07:00
Michael Haggerty
c21d39d7c7 Extract a struct stat_data from cache_entry
Add public functions fill_stat_data() and match_stat_data() to work
with it.  This infrastructure will later be used to check the validity
of other types of file.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:50:17 -07:00
Michael Haggerty
4f6b83e370 packed_ref_cache: increment refcount when locked
Increment the packed_ref_cache reference count while it is locked to
prevent its being freed.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:50:17 -07:00
Michael Haggerty
8baf2bb99a do_for_each_entry(): increment the packed refs cache refcount
This function calls a user-supplied callback function which could do
something that causes the packed refs cache to be invalidated.  So
acquire a reference count on the data structure to prevent our copy
from being freed while we are iterating over it.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-20 15:50:17 -07:00