A tree to index rename with no changes was getting erased by
the iteration routine (if the routine actually loaded the data
for the unmodified file).  This invokes the code path that was
previously messing up the diff and iterates twice to make sure
that the iteration process itself doesn't modify the data.

This changes the behavior of the status RENAMED flags so that they
will be combined with the MODIFIED flags if appropriate.  If a file
is modified in the index and also renamed, then the status code
will have both the GIT_STATUS_INDEX_MODIFIED and INDEX_RENAMED bits
set.  If it is renamed but the OID has not changed, then just the
GIT_STATUS_INDEX_RENAMED bit will be set.  Similarly, the flags
GIT_STATUS_WT_MODIFIED and GIT_STATUS_WT_RENAMED can both be set
independently of one another.

This fixes a serious bug where the check for unmodified files that
was done at data load time could end up erasing the RENAMED state
of a file that was renamed with no changes.

Lastly, this contains a bunch of new tests for status with renames,
including tests where the only rename changes are case changes.
The expected results of these tests have to vary by whether the
platform uses a case sensitive filesystem or not, so the expected
data covers those platform differences separately.

Trees are always case sensitive.  The index is always case
preserving and will be case sensitive when it is turned into a
tree.  Therefore the tree and the index can and should always
be compared to one another case sensitively.

This will restore the index to case insensitive order after the
diff has been generated.

Consider this a short-term fix.  The long term fix is to have the
index always stored both case sensitively and case insensitively
(at least on platforms that sometimes require case insensitivity).

In a case insensitive index, if you attempt to add a file from
disk with a different case pattern, the old case pattern in the
index should be preserved.

This fixes that (and a couple of minor warnings).

This commit reinstates some changes to git_diff__paired_foreach
that were discarded during the rebase (because the diff_output.c
file had gone away), and also adjusts the case insensitively
logic slightly to hopefully deal with either mismatched icase
diffs and other case insensitivity scenarios.

This makes diff more careful about picking the canonical path
when generating a delta so that it won't accidentally pick up a
case-mismatched path on a case-insensitive file system.  This
should make sure we use the "most accurate" case correct version
of the path (i.e. from the tree if possible, or the index if
need be).

The exclude submodules flag was not doing the right thing, in
that a file with no diff between the head and the index and just
a delete in the workdir could be excluded if submodules were
excluded.

This simplifies some documentation and hopefully makes a couple
of things easier to read.  Also, this rearrages the order in this
branch so that the overall diff against the trunk will hopefully
be a bit cleaner.

ref: free the last ref when cancelling git_branch_foreach()

Also fixed an assert typo on nulltoken's HEAD

Memzero stuffs

On Linux: fix a warning message related to the volatile qualifier (cast)
On Windows: use SecureZeroMemory()

On both, inline the call, so that no entry point can lead back to this "secure" memory zeroing.

Fix/build warnings

cmake: Add option to specify the name of the binary

This reverts commit 095bfd74.

Fix Windows warnings and missing prototypes

This fixes problems with missing function prototypes and 64-bit
data issues on Windows.

Keep data about source of similarity

Diff code reorg plus function context in diff headers

This makes the git_diff_patch definition private to diff_patch.c
and fixes a number of other header file naming inconsistencies to
use `git_` prefixes on functions and structures that are shared
between files.

This changes the size data to uint32_t, fixes the array growth
logic to use a simple 1.5x multiplier, and uses a generic inline
function for growing the array to make the git_array_alloc API
feel more natural (i.e. it returns a pointer to the new item).

This adds two new public APIs: git_diff_patch_from_blobs and
git_diff_patch_from_blob_and_buffer, plus it refactors the code
for git_diff_blobs and git_diff_blob_to_buffer so that they code
is almost entirely shared between these APIs, and adds tests for
the new APIs.

This adds real tests for user-configured diff drivers and in the
process found a bunch of bugs.

Add high(est) config level for application specific config files

Some tools use an extra level to maintain an application specific config files on top of the normal ones. Revision 16adc9fa broke this.

Signed-off-by: Sven Strickroth <email@cs-ware.de>

This implements the loading of regular expression pattern lists
for diff drivers that search for function context in that way.
This also changes the way that diff drivers update options and
interface with xdiff APIs to make them a little more flexible.