If OpenSSL is disabled on Mac the SHA1 implementation goes
to the CommonCrypto from the system. In this case we should
not include the generic hash impl. Otherwise there would be
duplicated impls which fail the build.

Increment refcount of newly added cache entries just like existing
entries looked up from the cache. Otherwise the new entry can be
evicted from the cache and destroyed while it's still in use.

Fixes #2869. If included file includes more files, it may reallocate
cfg_file->readers, hence invalidate not only `r` pointer, but `result`
pointer as well.

Don't try to strip trailing paths from the root directory on
Windows (trying to create `C:` will fail).

`p_stat` calls `git_win32_path_from_utf8`, which canonicalizes the
path.  Do not further try to modify the path, else we trim the
trailing slash from a root directory and try to access `C:` instead
of `C:/`.

Test to ensure that we can create a repository at the filesystem
root.  Introduces a new test environment variable,
`GITTEST_INVASIVE_FILESYSTEM` for tests that do terrible things like
escaping the clar sandbox and writing to the root directory.  It is
expected that the CI builds will enable this but that normal people
would not want this.

Follow-up to 4f91bfa3 ("Find libssh2 via pkg-config"): FindPkgConfig sets
<foo>_INCLUDE_DIRS, not <foo>_INCLUDE_DIR like FindLIBSSH2 did.

Additionally, if using only FindPkgConfig to find libssh2, we have to
call LINK_DIRECTORIES() as well to pass the appropriate -L entries,
otherwise the build will only work if libssh2.so is in a directory
searched automatically by the linker.

This fixes the build at least on FreeBSD, where those types were not
defined indirectly:

src/openssl_stream.c:100:18: error: variable has incomplete type 'struct in6_addr'
        struct in6_addr addr6;
                        ^
src/openssl_stream.c:100:9: note: forward declaration of 'struct in6_addr'
        struct in6_addr addr6;
               ^
src/openssl_stream.c:111:18: error: use of undeclared identifier 'AF_INET'
        if (p_inet_pton(AF_INET, host, &addr4)) {
                        ^
src/unix/posix.h:31:40: note: expanded from macro 'p_inet_pton'
                                       ^
src/openssl_stream.c:115:18: error: use of undeclared identifier 'AF_INET6'
                if(p_inet_pton(AF_INET6, host, &addr6)) {
                               ^
src/unix/posix.h:31:40: note: expanded from macro 'p_inet_pton'
                                       ^

It was missing "common.h" and "types.h" like other system headers.
This generated compilation errors if including it directly.

Main change: Don't treat chars > 128 as non-printable (common in UTF-8 files)

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

Fix build on mingw

It's currently required in src/openssl_stream.c only.

Windows headers #define some names that openssl uses too. Openssl
headers #undef the offending names before reusing them. But if those
offending Windows headers get included after the openssl headers the
namespace is polluted and nothing good happens.

Fixes issue #2850.

pathspec_match_free() should not dereference a NULL passed to it.

I found this issue when I tried to run example log program with
nonexistent branch:

./example/log help

Such call leads to segmentation fault.

On case insensitive filesystems, we may have files in the working
directory that case fold to a name we want to write.  Remove those
files (by default) so that we will not end up with a filename that
has the unexpected case.

Symbolic links that abuse case insensitivity to write into .git.

Don't bother trying to recreate the previously created directory
during checkout, for a modest reduction in the number of stats.

The documentation for `git_path_join_unrooted` states that the base
length will be returned, so that consumers like checkout know where
to start creating directories instead of always creating directories
at the directory root.

Checkout can now provide performance data about the number of (some)
syscalls performed using an optional callback.

This structure remains internal-only in maintenance branches.

clone example: don't divide by zero

Local transports don't have data about the size, avoid dividing by
zero in the callback.

This should provide a easier way to see what kinds of changes we have,
and a single place to look at the breaking changes.

  Fix crash in free() when git_buf_grow() fails.

Remove symlinks from the repository

remote: plug leak