log: use true parents for diff even when rewriting

When using pathspec filtering in combination with diff-based log
output, parent simplification happens before the diff is computed.
The diff is therefore against the *simplified* parents.

This works okay, arguably by accident, in the normal case:
simplification reduces to one parent as long as the commit is TREESAME
to it.  So the simplified parent of any given commit must have the
same tree contents on the filtered paths as its true (unfiltered)
parent.

However, --full-diff breaks this guarantee, and indeed gives pretty
spectacular results when comparing the output of

  git log --graph --stat ...
  git log --graph --full-diff --stat ...

(--graph internally kicks in parent simplification, much like
--parents).

To fix it, store a copy of the parent list before simplification (in a
slab) whenever --full-diff is in effect.  Then use the stored parents
instead of the simplified ones in the commit display code paths.  The
latter do not actually check for --full-diff to avoid duplicated code;
they just grab the original parents if save_parents() has not been
called for this revision walk.

For ordinary commits it should be obvious that this is the right thing
to do.

Merge commits are a bit subtle.  Observe that with default
simplification, merge simplification is an all-or-nothing decision:
either the merge is TREESAME to one parent and disappears, or it is
different from all parents and the parent list remains intact.
Redundant parents are not pruned, so the existing code also shows them
as a merge.

So if we do show a merge commit, the parent list just consists of the
rewrite result on each parent.  Running, e.g., --cc on this in
--full-diff mode is not very useful: if any commits were skipped, some
hunks will disagree with all sides of the merge (with one side,
because commits were skipped; with the others, because they didn't
have those changes in the first place).  This triggers --cc showing
these hunks spuriously.

Therefore I believe that even for merge commits it is better to show
the diffs wrt. the original parents.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
log: use true parents for diff when walking reflogs

The reflog walking logic (git log -g) replaces the true parent list
with the preceding commit in the reflog.  This results in bogus commit
diffs when combined with options such as -p; the diff is against the
reflog predecessor, not the parent of the commit.

Save the true parents on the side, extending the functions from the
previous commit.  The diff logic picks them up and uses them to show
the correct diffs.

We do have to be somewhat careful about repeated calling of
save_parents(), since the reflog may list a commit more than once.  We
now store (commit_list*)-1 to distinguish the "not saved yet" and
"root commit" cases.  This lets us preserve an empty parent list even
if save_parents() is repeatedly called.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
die_with_status: use "printf '%s\n'", not "echo"

Some implementations of 'echo' (e.g. dash's built-in) interpret
backslash sequences in their arguments.

This triggered at least one bug: the error message of "rebase -i" was
turning \t in commit messages into actual tabulations. There may be
others.

Using "printf '%s\n'" instead avoids this bad behavior, and is the form
used by the "say" function.

Noticed-by: David Kastrup <dak@gnu.org>
Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t5802: add test for connect helper

This is an attempt to reproduce a problem reported for a third-party
custom "connect" remote helper.  The conjecture is that sometimes
"git fetch" wants to make two connections (one for the primary
transfer with 'follow-tags' option set, and then after noticing that
some tags are not packed because the primary transfer did not have
to send any commit that is pointed by them, another to explicitly
ask for the missing tags), and their "connect" helper is not called
in the second request, breaking the "fetch" as a whole.

Unfortunately this test script does not trigger the alleged failure
and happily passes when talking to upload-pack from git-core (see
patch 5/5 for details).

Signed-off-by: Junio C Hamano <gitster@pobox.com>
fetch: rename file-scope global "transport" to "gtransport"

Although many functions in this file take a "struct transport" as a
parameter, "fetch_one()" assigns to the global singleton instance
which is a file-scope static, in order to allow a parameterless
signal handler unlock_pack() to access it.

Rename the variable to gtransport to make sure these uses stand out.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
fetch: refactor code that prepares a transport

Make a helper function prepare_transport() that returns a transport
to talk to a given remote.

The set_option() helper that used to always affect the file-scope
global "gtransport" now takes a transport as its parameter.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
fetch: refactor code that fetches leftover tags

Usually the upload-pack process running on the other side will give
us all the reachable tags we need during the primary object transfer
in do_fetch().  If that does not happen (e.g. the other side may be
running a third-party implementation of upload-pack), we will run
another fetch to pick up leftover tags that we know point at the
commits reachable from our updated tips.

Separate out the code to run this second fetch into a helper
function.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
fetch: work around "transport-take-over" hack

A Git-aware "connect" transport allows the "transport_take_over" to
redirect generic transport requests like fetch(), push_refs() and
get_refs_list() to the native Git transport handling methods.  The
take-over process replaces transport->data with a fake data that
these method implementations understand.

While this hack works OK for a single request, it breaks when the
transport needs to make more than one requests.  transport->data
that used to hold necessary information for the specific helper to
work correctly is destroyed during the take-over process.

One codepath that this matters is "git fetch" in auto-follow mode;
when it does not get all the tags that ought to point at the history
it got (which can be determined by looking at the peeled tags in the
initial advertisement) from the primary transfer, it internally
makes a second request to complete the fetch.  Because "take-over"
hack has already destroyed the data necessary to talk to the
transport helper by the time this happens, the second request cannot
make a request to the helper to make another connection to fetch
these additional tags.

Mark such a transport as "cannot_reuse", and use a separate
transport to perform the backfill fetch in order to work around
this breakage.

Note that this problem does not manifest itself when running t5802,
because our upload-pack gives you all the necessary auto-followed
tags during the primary transfer.  You would need to step through
"git fetch" in a debugger, stop immediately after the primary
transfer finishes and writes these auto-followed tags, remove the
tag references and repack/prune the repository to convince the
"find-non-local-tags" procedure that the primary transfer failed to
give us all the necessary tags, and then let it continue, in order
to trigger the bug in the secondary transfer this patch fixes.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
avoid segfault on submodule.*.path set to an empty "true"

Git fails due to a segmentation fault if a submodule path is empty.
Here is an example .gitmodules that will cause a segmentation fault:

    [submodule "foo-module"]
      path
      url = http://host/repo.git
    $ git status
    Segmentation fault (core dumped)

This is because the parsing of "submodule.*.path" is not prepared to
see a value-less "true" and assumes that the value is always
non-NULL (parsing of "ignore" has the same problem).

Fix it by checking the NULL-ness of value and complain with
config_error_nonbool().

Signed-off-by: Jharrod LaFon <jlafon@eyesopen.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
xread, xwrite: limit size of IO to 8MB

Checking out 2GB or more through an external filter (see test) fails
on Mac OS X 10.8.4 (12E55) for a 64-bit executable with:

    error: read from external filter cat failed
    error: cannot feed the input to external filter cat
    error: cat died of signal 13
    error: external filter cat failed 141
    error: external filter cat failed

The reason is that read() immediately returns with EINVAL when asked
to read more than 2GB.  According to POSIX [1], if the value of
nbyte passed to read() is greater than SSIZE_MAX, the result is
implementation-defined.  The write function has the same restriction
[2].  Since OS X still supports running 32-bit executables, the
32-bit limit (SSIZE_MAX = INT_MAX = 2GB - 1) seems to be also
imposed on 64-bit executables under certain conditions.  For write,
the problem has been addressed earlier [6c642a].

Address the problem for read() and write() differently, by limiting
size of IO chunks unconditionally on all platforms in xread() and
xwrite().  Large chunks only cause problems, like causing latencies
when killing the process, even if OS X was not buggy.  Doing IO in
reasonably sized smaller chunks should have no negative impact on
performance.

The compat wrapper clipped_write() introduced earlier [6c642a] is
not needed anymore.  It will be reverted in a separate commit.  The
new test catches read and write problems.

Note that 'git add' exits with 0 even if it prints filtering errors
to stderr.  The test, therefore, checks stderr.  'git add' should
probably be changed (sometime in another commit) to exit with
nonzero if filtering fails.  The test could then be changed to use
test_must_fail.

Thanks to the following people for suggestions and testing:

    Johannes Sixt <j6t@kdbg.org>
    John Keeping <john@keeping.me.uk>
    Jonathan Nieder <jrnieder@gmail.com>
    Kyle J. McKay <mackyle@gmail.com>
    Linus Torvalds <torvalds@linux-foundation.org>
    Torsten Bögershausen <tboegi@web.de>

[1] http://pubs.opengroup.org/onlinepubs/009695399/functions/read.html
[2] http://pubs.opengroup.org/onlinepubs/009695399/functions/write.html

[6c642a] commit 6c642a878688adf46b226903858b53e2d31ac5c3
    compate/clipped-write.c: large write(2) fails on Mac OS X/XNU

Signed-off-by: Steffen Prohaska <prohaska@zib.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Revert "compat/clipped-write.c: large write(2) fails on Mac OS X/XNU"

This reverts commit 6c642a878688adf46b226903858b53e2d31ac5c3.

The previous commit introduced a size limit on IO chunks on all
platforms.  The compat clipped_write() is not needed anymore.

Signed-off-by: Steffen Prohaska <prohaska@zib.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-completion.bash: use correct Bash/Zsh array length syntax

The syntax for retrieving the number of elements in an array is:

   ${#name[@]}

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t9902-completion.sh: old Bash still does not support array+=('') notation

Old Bash (3.0) which is distributed with RHEL 4.X and other ancient
platforms that are still in wide use, does not understand the
array+=() notation.  Let's use an explicit assignment to the new array
element which works everywhere, like:

   array[${#array[@]}+1]=''

The right-hand side '' is not strictly necessary, but in this case
I think it is more clear.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
contrib/git-prompt.sh: handle missing 'printf -v' more gracefully

Old Bash (3.0) which is distributed with RHEL 4.X and other ancient
platforms that are still in wide use, do not have a printf that
supports -v.  Neither does Zsh (which is already handled in the code).

As suggested by Junio, let's test whether printf supports the -v
option and store the result.  Then later, we can use it to
determine whether 'printf -v' can be used, or whether printf
must be called in a subshell.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
mailmap: handle mailmap blobs without trailing newlines

The read_mailmap_buf function reads each line of the mailmap
using strchrnul, like:

    const char *end = strchrnul(buf, '\n');
    unsigned long linelen = end - buf + 1;

But that's off-by-one when we actually hit the NUL byte; our
line does not have a terminator, and so is only "end - buf"
bytes long. As a result, when we subtract the linelen from
the total len, we end up with (unsigned long)-1 bytes left
in the buffer, and we start reading random junk from memory.

We could fix it with:

    unsigned long linelen = end - buf + !!*end;

but let's take a step back for a moment. It's questionable
in the first place for a function that takes a buffer and
length to be using strchrnul. But it works because we only
have one caller (and are only likely to ever have this one),
which is handing us data from read_sha1_file. Which means
that it's always NUL-terminated.

Instead of tightening the assumptions to make the
buffer/length pair work for a caller that doesn't actually
exist, let's let loosen the assumptions to what the real
caller has: a modifiable, NUL-terminated string.

This makes the code simpler and shorter (because we don't
have to correlate strchrnul with the length calculation),
correct (because the code with the off-by-one just goes
away), and more efficient (we can drop the extra allocation
we needed to create NUL-terminated strings for each line,
and just terminate in place).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
builtin/fetch.c: Fix a sparse warning

Sparse issues an "'prepare_transport' was not declared. Should it
be static?" warning. In order to suppress the warning, since this
symbol only requires file scope, we simply add the static modifier
to it's declaration.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'jk/mailmap-incomplete-line' into maint

* jk/mailmap-incomplete-line:
  mailmap: handle mailmap blobs without trailing newlines
Merge branch 'sp/clip-read-write-to-8mb' into maint

Send a large request to read(2)/write(2) as a smaller but still
reasonably large chunks, which would improve the latency when the
operation needs to be killed and incidentally works around broken
64-bit systems that cannot take a 2GB write or read in one go.

* sp/clip-read-write-to-8mb:
  Revert "compat/clipped-write.c: large write(2) fails on Mac OS X/XNU"
  xread, xwrite: limit size of IO to 8MB
Merge branch 'jc/transport-do-not-use-connect-twice-in-fetch' into maint

The auto-tag-following code in "git fetch" tries to reuse the same
transport twice when the serving end does not cooperate and does
not give tags that point to commits that are asked for as part of
the primary transfer.  Unfortunately, Git-aware transport helper
interface is not designed to be used more than once, hence this
does not work over smart-http transfer.

* jc/transport-do-not-use-connect-twice-in-fetch:
  builtin/fetch.c: Fix a sparse warning
  fetch: work around "transport-take-over" hack
  fetch: refactor code that fetches leftover tags
  fetch: refactor code that prepares a transport
  fetch: rename file-scope global "transport" to "gtransport"
  t5802: add test for connect helper
Merge branch 'tr/log-full-diff-keep-true-parents' into maint

Output from "git log --full-diff -- <pathspec>" looked strange,
because comparison was done with the previous ancestor that touched
the specified <pathspec>, causing the patches for paths outside the
pathspec to show more than the single commit has changed.

* tr/log-full-diff-keep-true-parents:
  log: use true parents for diff when walking reflogs
  log: use true parents for diff even when rewriting