When concluding a conflicted "git merge --squash", the command
failed to read SQUASH_MSG that was prepared by "git merge", and
showed only the "# Conflicts:" list of conflicted paths.

Place the contents from SQUASH_MSG at the beginning, just like we
show the commit log skeleton first when concluding a normal merge,
and then show the "# Conflicts:" list, to help the user write the
log message for the resulting commit.

Test by Junio C Hamano <gitster@pobox.com>.

Signed-off-by: Sven Strickroth <sven@cs-ware.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

One of the most common uses of git_path() is to pass a
constant, like git_path("MERGE_MSG"). This has two
drawbacks:

  1. The return value is a static buffer, and the lifetime
     is dependent on other calls to git_path, etc.

  2. There's no compile-time checking of the pathname. This
     is OK for a one-off (after all, we have to spell it
     correctly at least once), but many of these constant
     strings appear throughout the code.

This patch introduces a series of functions to "memoize"
these strings, which are essentially globals for the
lifetime of the program. We compute the value once, take
ownership of the buffer, and return the cached value for
subsequent calls.  cache.h provides a helper macro for
defining these functions as one-liners, and defines a few
common ones for global use.

Using a macro is a little bit gross, but it does nicely
document the purpose of the functions. If we need to touch
them all later (e.g., because we learned how to change the
git_dir variable at runtime, and need to invalidate all of
the stored values), it will be much easier to have the
complete list.

Note that the shared-global functions have separate, manual
declarations. We could do something clever with the macros
(e.g., expand it to a declaration in some places, and a
declaration _and_ a definition in path.c). But there aren't
that many, and it's probably better to stay away from
too-magical macros.

Likewise, if we abandon the C preprocessor in favor of
generating these with a script, we could get much fancier.
E.g., normalizing "FOO/BAR-BAZ" into "git_path_foo_bar_baz".
But the small amount of saved typing is probably not worth
the resulting confusion to readers who want to grep for the
function's definition.

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

The get_repo_path function calls mkpath() and then does some
non-trivial operations on it, like calling
is_git_directory() and read_gitfile(). These are actually
OK (they do not use more pathname static buffers
themselves), but it takes a fair bit of work to verify.

Let's use our own strbuf to store the path, and we can
simply reuse it for each iteration of the loop (we can even
avoid rewriting the beginning part, since we are trying a
series of suffixes).

To make the strbuf cleanup easier, we split out a thin
wrapper. As a bonus, this wrapper can factor out the
canonicalization that happens in all of the early-return
code paths.

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

It's an anti-pattern to assign the result of git_path to a
variable, since other calls may reuse our buffer. In this
case, we feed the result to unlink_or_warn immediately
afterwards, so it's OK. However, it's nice to avoid
assignment entirely, which makes it more obvious that
there's no bug.

We can just pass the result directly to unlink_or_warn,
which is a known-simple function. As a bonus, the code flow
is a little more obvious, as we eliminate an extra
conditional (a reader does not have to wonder any more
"under which circumstances is 'path' set?").

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

As with the previous commit to git_path, assigning the
result of mkpath is suspicious, since it is not clear
whether we will still depend on the value after it may have
been overwritten by subsequent calls. This patch converts
low-hanging fruit to use mkpathdup instead of mkpath (with
the downside that we must remember to free the result).

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

Because git_path uses a static buffer that is shared with
calls to git_path, mkpath, etc, it can be dangerous to
assign the result to a variable or pass it to a non-trivial
function. The value may change unexpectedly due to other
calls.

None of the cases changed here has a known bug, but they're
worth converting away from git_path because:

  1. It's easy to use git_pathdup in these cases.

  2. They use constructs (like assignment) that make it
     hard to tell whether they're safe or not.

The extra malloc overhead should be trivial, as an
allocation should be an order of magnitude cheaper than a
system call (which we are clearly about to make, since we
are constructing a filename). The real cost is that we must
remember to free the result.

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

An attempt to delete a ref by pushing into a repositorywhose HEAD
symbolic reference points at an unborn branch that cannot be
created due to ref D/F conflict (e.g. refs/heads/a/b exists, HEAD
points at refs/heads/a) failed.

* jx/do-not-crash-receive-pack-wo-head:
  receive-pack: crash when checking with non-exist HEAD

The low-level "git send-pack" did not honor 'user.signingkey'
configuration variable when sending a signed-push.

* db/send-pack-user-signingkey:
  builtin/send-pack.c: respect user.signingkey

In preparation for allowing different "backends" to store the refs
in a way different from the traditional "one ref per file in $GIT_DIR
or in a $GIT_DIR/packed-refs file" filesystem storage, reduce
direct filesystem access to ref-like things like CHERRY_PICK_HEAD
from scripts and programs.

* dt/refs-backend-preamble:
  git-stash: use update-ref --create-reflog instead of creating files
  update-ref and tag: add --create-reflog arg
  refs: add REF_FORCE_CREATE_REFLOG flag
  git-reflog: add exists command
  refs: new public ref function: safe_create_reflog
  refs: break out check for reflog autocreation
  refs.c: add err arguments to reflog functions

Teach "git log" and friends a new "--date=format:..." option to
format timestamps using system's strftime(3).

* jk/date-mode-format:
  strbuf: make strbuf_addftime more robust
  introduce "format" date-mode
  convert "enum date_mode" into a struct
  show-branch: use DATE_RELATIVE instead of magic number