The normal way to check whether a certain revision resolves to a valid
commit is:

  $ git rev-parse --verify $REV^0

Unfortunately, this does not work when $REV is of the type :/quuxery.
Write a helper to work around this limitation.

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Adjust the order mergetools feeds the files to the p4merge backend
to match the p4 convention.

* kb/p4merge:
  merge-one-file: force content conflict for "both sides added" case
  git-merge-one-file: send "ERROR:" messages to stderr
  git-merge-one-file: style cleanup
  merge-one-file: remove stale comment
  mergetools/p4merge: create a base if none available
  mergetools/p4merge: swap LOCAL and REMOTE

Originally, with no base, Git gave P4Merge $LOCAL as a dummy base:

   p4merge "$LOCAL" "$LOCAL" "$REMOTE" "$MERGED"

Commit 0a0ec7bd changed this to:

   p4merge "empty file" "$LOCAL" "$REMOTE" "$MERGED"

to avoid the problem of being unable to save in some circumstances with
similar inputs.

Unfortunately this approach produces much worse results on differing
inputs. P4Merge really regards the blank file as the base, and once you
have just a couple of differences between the two branches you end up
with one a massive full-file conflict. The 3-way diff is not readable,
and you have to invoke "difftool MERGE_HEAD HEAD" manually to get a
useful view.

The original approach appears to have invoked special 2-way merge
behaviour in P4Merge that occurs only if the base filename is "" or
equal to the left input.  You get a good visual comparison, and it does
not auto-resolve differences. (Normally if one branch matched the base,
it would autoresolve to the other branch).

But there appears to be no way of getting this 2-way behaviour and being
able to reliably save. Having base==left appears to be triggering other
assumptions. There are tricks the user can use to force the save icon
on, but it's not intuitive.

So we now follow a suggestion given in the original patch's discussion:
generate a virtual base, consisting of the lines common to the two
branches. This is the same as the technique used in resolve and octopus
merges, so we relocate that code to a shared function.

Note that if there are no differences at the same location, this
technique can lead to automatic resolution without conflict, combining
everything from the 2 files.  As with the other merges using this
technique, we assume the user will inspect the result before saving.

Signed-off-by: Kevin Bracey <kevin@bracey.fi>
Reviewed-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

mergetool, bisect, and other commands that use
git-sh-setup print a usage string that is inconsistent
with the rest of Git when they are invoked as "git $cmd -h".

The compiled builtins use the lowercase "usage:" string
but these commands say "Usage:".  Adjust the shell library
to make these consistent.

Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Some shells do not behave correctly when IFS is unset; work it
around by explicitly setting it to the default value.

* jc/maint-fbsd-sh-ifs-workaround:
  sh-setup: work around "unset IFS" bug in some shells

With an unset IFS, field splitting is supposed to act as if IFS is
set to the usual SP HT LF, but Marc Branchaud reports that the shell
on FreeBSD 7.2 gets this wrong.

It is easy to set it to the default value manually, and it is also
safer in case somebody tries to save the old value away and restore,
e.g.

	$oIFS=$IFS
	IFS=something
	...
	IFS=$oIFS

while forgetting that the original IFS might be unset (which can be
coded but would be more involved).

Signed-off-by: Junio C Hamano <gitster@pobox.com>

The only ident-parsing function we currently provide is
get_author_ident_from_commit. This is not very
flexible for two reasons:

  1. It takes a commit as an argument, and can't read from
     commit headers saved on disk.

  2. It will only parse authors, not committers.

This patch provides a more flexible interface which will
parse multiple idents from a commit provide on stdin. We can
easily use it as a building block for the current function
to retain compatibility.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

When the user exports a non-default IFS without HT, scripts that
rely on being able to parse "ls-files -s | while read a b c..."
start to fail.  Protect them from such a misconfiguration.

* jc/maint-protect-sh-from-ifs:
  sh-setup: protect from exported IFS

Many scripted Porcelains rely on being able to split words at the
default $IFS characters, i.e. SP, HT and LF.  If the user exports a
non-default IFS to the environment, what they read from plumbing
commands such as ls-files that use HT to delimit fields may not be
split in the way we expect.

Protect outselves by resetting it, just like we do so against CDPATH
exported to the environment.

Noticed by Andrew Dranse <adranse@oanda.com>.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Recently we tweaked this scriptlet to let mingw port redefine "pwd" to
always return Windows-style path, but the code to do so came after the
first use of "pwd" to set up $GIT_DIR shell variable.

Move the block to define these workaround wrappers, so that everything
everything that executes when the scriptlet is dot-sourced uses the
replacements.

Noticed-by: Ramsay Jones
Signed-off-by: Junio C Hamano <gitster@pobox.com>