When compiling libgit2 with -DDEPRECATE_HARD, we add a preprocessor
definition `GIT_DEPRECATE_HARD` which causes the "git2/deprecated.h"
header to be empty. As a result, no function declarations are made
available to callers, but the implementations are still available to
link against. This has the problem that function declarations also
aren't visible to the implementations, meaning that the symbol's
visibility will not be set up correctly. As a result, the resulting
library may not expose those deprecated symbols at all on some platforms
and thus cause linking errors.

Fix the issue by conditionally compiling deprecated functions, only.
While it becomes impossible to link against such a library in case one
uses deprecated functions, distributors of libgit2 aren't expected to
pass -DDEPRECATE_HARD anyway. Instead, users of libgit2 should manually
define GIT_DEPRECATE_HARD to hide deprecated functions. Using "real"
hard deprecation still makes sense in the context of CI to test we don't
use deprecated symbols ourselves and in case a dependant uses libgit2 in
a vendored way and knows it won't ever use any of the deprecated symbols
anyway.

We've accumulated quite some functions which are never used outside of
their respective code unit, but which are lacking the `static` keyword.
Add it to reduce their linkage scope and allow the compiler to optimize
better.

We have some functions which aren't used anywhere. Let's remove them to
get rid of unneeded baggage.

Current implementation of patchid is not computing a correct patchid
when given a patch where, for example, a new file is added or removed.
Some more corner cases need to be handled to have same behavior as git
patch-id command.
Add some more tests to cover those corner cases.

Signed-off-by: Gregory Herrero <gregory.herrero@oracle.com>

Using an `enum` causes trouble when used with C++ as bitwise operations are not possible w/o casting (e.g., `opts.flags &= ~GIT_BLOB_FILTER_CHECK_FOR_BINARY;` is invalid as there is no `&=` operator for `enum`).

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

The patch ID is supposed to be mostly context-insignificant and
thus only includes added or deleted lines. As such, we shouldn't honor
end-of-file-without-newline markers in diffs.

Ignore such lines to fix how we compute the patch ID for such diffs.

In libgit2 nomenclature, when we need to verb a direct object, we name
a function `git_directobject_verb`.  Thus, if we need to init an options
structure named `git_foo_options`, then the name of the function that
does that should be `git_foo_options_init`.

The previous names of `git_foo_init_options` is close - it _sounds_ as
if it's initializing the options of a `foo`, but in fact
`git_foo_options` is its own noun that should be respected.

Deprecate the old names; they'll now call directly to the new ones.

Quiet down a warning from MSVC about how we're potentially losing data.

Move to the `git_error` name in the internal API for error-related
functions.