Adding a new config iteration function that let's you iterate
over just the config entries that match a particular regular
expression.  The old foreach becomes a simple use of this with
an empty pattern.

This also fixes an apparent bug in the existing `git_config_foreach`
where returning a non-zero value from the iteration callback was
not correctly aborting the iteration and the returned value was
not being propogated back to the caller of foreach.

Added to tests to cover all these changes.

Adding 0x85 to `git__isspace` since we also look for that in filter.c
as a whitespace character.

This makes it easy to take a buffer containing a path with relative
references (i.e. .. or . path segments) and resolve all of those
into a clean path.  This can be applied to URLs as well as file
paths which can be useful.

As part of this, I made the drive-letter detection apply on all
platforms, not just windows.  If you give a path that looks like
"c:/..." on any platform, it seems like we might as well detect
that as a rooted path.  I suppose if you create a directory named
"x:" on another platform and want to use that as the beginning
of a relative path under the root directory of your repo, this
could cause a problem, but then it seems like you're asking for
trouble.

* `git_buf_rfind` (with tests and tests for `git_buf_rfind_next`)
* `git_buf_puts_escaped` and `git_buf_puts_escaped_regex` (with tests)
  to copy strings into a buffer while injecting an escape sequence
  (e.g. '\') in front of particular characters.

examples: add README

Bring back `entry_bypath`

diff: make inter-hunk-context default value git-compliant

Point to the libgit2-glib wiki page

Fix libgit2 on GNU/Hurd.

On GNU, the d_name field of the dirent structure is defined as "char d_name[1]",
so we must allocate more than sizeof(struct dirent) bytes, just like on Sun.

revparse: fix parsing of date specifiers

Replace incorrect 'it' with 'if' in documentation

Default in git core is 0, not 3

More git_revparse_single ENOTFOUND use cases

It causes the clar testsuite to abort on Windows, and isn't necessary.

Smaller, simpler, faster.

Small revparse colon syntax improvements

Once a file is registered, there is no way to deregister it, even
after the structure that contains it is no longer needed and has been
freed. This may be the source of #624.

Allow and use the deregister function to remove our file from the
global list.

indexer: don't use '/objects/pack/' unconditionally

Not everyone who indexes a packfile wants to put it in the standard
git repository location.

Repo reinit fix + enhanced test coverage

Topic/refs fromglob

indexer: start parsing input data immediately

Currently, the first call of git_indexer_stream_add adds the data to the
underlying pack file and opens it for later use, but doesn't start
parsing the already available data.
This means, git_indexer_stream_finalize only works if
git_indexer_stream_add was called at least twice. Kill this limitation
by parsing available data immediately.