Add support for git attribute macro definitions.  Also, add
support for cache flush API to clear the attribute file content
cache when needed.

Additionally, improved the handling of global and system files,
making common utility functions in fileops and converting config
and attr to both use the common functions.

Adds a bunch more tests and fixed some memory leaks.  Note that
adding macros required me to use refcounted attribute assignment
definitions, which complicated, but probably improved memory usage.

This adds APIs for querying git attributes.  In addition to
the new API in include/git2/attr.h, most of the action is in
src/attr_file.[hc] which contains utilities for dealing with
a single attributes file, and src/attr.[hc] which contains
the implementation of the APIs that merge all applicable
attributes files.

In an effort to remove duplicate code, I accidentally left
the stat structure uninitialized in this function.  This
patch restores that data gathering.

Really delete variables

Instead of just setting the value to NULL, which gives unwanted
results when asking for that variable after deleting it, delete the
variable from the list and re-write the file.

This would make us think that config variables like

    [core]
        something

is missing.

Comes with support for global events; this fixes #496.

It was not safe for git_buf_joinpath to be used with a pointer
into the buf itself because a reallocation could invalidate
the input parameter that pointed into the buffer.  This patch
makes it safe to self join, at least for the leading input to
the join, which is the common "append" case for self joins.

Also added unit tests to explicitly cover this case.

This should actually fix #511

This commit fixes #511.

commit: add test to ensure predictability of generation of commit, tree and blob object ids

Prevent segfaulting on Windows when building a temporary filename

Conflicts:
	tests-clay/clay.h
	tests-clay/clay_main.c

Conflicts:
	tests-clay/clay_main.c

This converts virtually all of the places that allocate GIT_PATH_MAX
buffers on the stack for manipulating paths to use git_buf objects
instead.  The patch is pretty careful not to touch the public API
for libgit2, so there are a few places that still use GIT_PATH_MAX.

This extends and changes some details of the git_buf implementation
to add a couple of extra functions and to make error handling easier.

This includes serious alterations to all the path.c functions, and
several of the fileops.c ones, too.  Also, there are a number of new
functions that parallel existing ones except that use a git_buf
instead of a stack-based buffer (such as git_config_find_global_r
that exists alongsize git_config_find_global).

This also modifies the win32 version of p_realpath to allocate whatever
buffer size is needed to accommodate the realpath instead of hardcoding
a GIT_PATH_MAX limit, but that change needs to be tested still.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>
Signed-off-by: Vicent Marti <tanoku@gmail.com>

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Author:    Carlos Martín Nieto <carlos@cmartin.tk>
#
# On branch development
# Your branch is ahead of 'origin/development' by 11 commits.
#
# Changes to be committed:
#   (use "git reset HEAD^1 <file>..." to unstage)
#
#	modified:   include/git2/tree.h
#	modified:   src/tree.c
#	modified:   tests-clay/clay_main.c
#	modified:   tests-clay/object/tree/diff.c
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#	0001-remote-Cleanup-the-remotes-code.patch
#	466.patch
#	466.patch.1
#	488.patch
#	Makefile
#	libgit2.0.15.0.dylib
#	libgit2.0.dylib
#	libgit2.dylib
#	libgit2_clay
#	libgit2_test
#	tests-clay/object/tree/

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>
Signed-off-by: Vicent Marti <tanoku@gmail.com>

For each difference in the trees, the callback gets called with the
relevant information so the user can fill in their own data
structures.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

Fix compilation warnings

Optimized implementation of git_buf_join

This streamlines git_buf_join and removes the join-append behavior,
opting instead for a very compact join-replace of the git_buf contents.
The unit tests had to be updated to remove the join-append tests and
have a bunch more exhaustive tests added.

Make git_buf functions always maintain a valid cstr

Taking a page from core git's strbuf, this introduces git_buf_initbuf
which is an empty string that is used to initialize the git_buf ptr
value even for new buffers.  Now the git_buf ptr will always point to
a valid NUL-terminated string.

This change required jumping through a few hoops for git_buf_grow
and git_buf_free to distinguish between a actual allocated buffer
and the global initial value.  Also, this moves the allocation
related functions to be next to each other near the top of buffer.c.

At a tiny cost of 1 extra byte per allocation, this makes
git_buf_cstr into basically a noop, which simplifies error
checking when trying to convert things to use dynamic allocation.

This patch also adds a new function (git_buf_copy_cstr) for copying
the cstr data directly into an external buffer.

Minor fixups

Actually add the tests introduced with 8c74d22e.

Signed-off-by: schu <schu-github@schulog.org>

Signed-off-by: schu <schu-github@schulog.org>

Extend git_buf with new utility functions and unit tests.

* replace some ints with size_ts
* update NULL checks in various places