A number of source files have their implementation #ifdef'd out (because
they target another platform).  MSVC warns on empty compilation units
(with warning LNK4221).  Ignore warning 4221 when creating the object
library.

Cast actual filesystem data to the int32_t that index entries store.

The filesystem iterator takes `stat` data from disk and puts them into
index entries, which use 32 bit ints for time (the seconds portion) and
filesize.  However, on most systems these are not 32 bit, thus will
typically invoke a warning.

Most users ignore these fields entirely.  Diff and checkout code do use
the values, however only for the cache to determine if they should check
file modification.  Thus, this is not a critical error (and will cause a
hash recomputation at worst).

Our blob size is a `git_off_t`, which is a signed 64 bit int.  This may
be erroneously negative or larger than `SIZE_MAX`.  Ensure that the blob
size fits into a `size_t` before casting.

Quiet down a warning from MSVC about how we're potentially losing data.
Ensure that we're within a uint16_t before we do.

Quiet down a warning from MSVC about how we're potentially losing data.
This is safe since we've explicitly tested that it's positive and less
than SIZE_MAX.

Quiet down a warning from MSVC about how we're potentially losing data.
This is safe since we've explicitly tested that it's within the range of
0-100.

Quiet down a warning from MSVC about how we're potentially losing data.
This cast is safe since we've explicitly tested that `strip_len` <=
`last_len`.

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

index: preserve extension parsing errors

Deprecate functions and constants more gently

Ensure that we do not use any deprecated functions in the library
source, test code or examples.

Users can define `GIT_DEPRECATE_HARD` if they want to remove all
functions that we've "softly" deprecated.

Move the deprecated stream tests into their own compilation unit.  This
will allow us to disable any preprocessor directives that apply to
deprecation just for these tests (eg, disabling `GIT_DEPRECATED_HARD`).

Avoid the deprecated `git_stream_cb` typedef since we want to compile
the library without deprecated functions or types.  Instead, we can
unroll the alias to its actual type.

Add `@deprecated` to the functions that are, so that they'll appear that
way in docurium.

`git_stream_register_tls` is now deprecated; mark it in an if guard with
the deprecation.

This should not be included in `deprecated.h` since it is an uncommonly
used `sys` header file.

Don't use deprecated constants

Follow up for PR #4917.

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

Previously, we would clobber any extension-specific error message with
an "extension is truncated" message. This makes `read_extension`
correctly preserve those errors, takes responsibility for truncation
errors, and adds a new message with the actual extension signature for
unsupported mandatory extensions.

Fix VS warning C4098: 'giterr_set_str' : void function returning a value

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

Move `giterr` to `git_error`

Update GITERR and giterr usages in the static code analysis tools to use
the new names.

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

Replace the `GITERR` values with a `const int` to deprecate error
values.

Move to the `git_error` name in error-related functions, deprecating the
`giterr` functions.  This means, for example, that `giterr_last` is now
`git_error_last`.  The old names are retained for compatibility.

This only updates the public API; internal API and function usage
remains unchanged.

odb: Fix odb foreach to also close on positive error code

In include/git2/odb.h it states that callback can also return
positive value which should break looping.

Implementations of git_odb_foreach() and pack_backend__foreach()
did not respect that.

repository: free memory in symlink detection function

ci: update poxyproxy, run in quiet mode