When ignoring a path "foo/", ensure that this is actually a directory,
and not simply a file named "foo".

When a .gitignore specifies some folder "foo/", ensure that a file
with the same name "foo" is not ignored.

Ensure that when examining a .gitignore in a subdirectory, we do not
erroneously apply the paths contained therein to the root of the
repository.  (Fixed in c02a0e46).

Centralizing all IO buffer size values

Stash apply

Allow the baseline to be specified as an index, so that users
need not write their index to a tree just to checkout with that
as the baseline.

Adjusting stream buffer size to 64KB

64K is optimal buffer size per https://technet.microsoft.com/en-us/library/cc938632.aspx

Android build doesn't need deps/regex

Ensure frameworks are mentioned in libgit2.pc

When building on Mac OS X, the `CoreFoundation` and `Security` frameworks where missing from `Libs.private` in the generated `libgit2.pc` file.

deps/regex was included in Android build because Android NDK 4 has
a packaging bug and doesn't have the regular expression functions defined
in its libc.so. The bug has been fixed in subsequent Android NDK releases.

If it is still necessary to work around the bug in Android NDK 4, we
should consider to use an option like ANDROID_NDK_RELEASE or
ANDROID_NDK_RELEASE_NUM.

Configuration changes for handling multiple of the same sections

Case insensitive checkout improvements

If a multivar exists within two sections (of the same name)
then they should both be updated in a `set_multivar`.  Ensure
that this is the case.

When writing a configuration file, we want to take a lock on the
new file (eg, `config.lock`) before opening the configuration file
(`config`) for reading so that we can prevent somebody from changing
the contents underneath us.

Add a test that exposes a bug in config_write.
It is valid to have multiple separate headers for the same config section, but
config_write will exit after finding the first matching section in certain
situations.
This test proves that config_write will duplicate a variable that already
exists instead of overwriting it if the variable is defined under a duplicate
section header.

When updating a configuration file, we want to copy the old data
from the file to preserve comments and funny whitespace, instead
of writing it in some "canonical" format.  Thus, we keep a
pointer to the start of the line and the line length to preserve
these things we don't care to rewrite.