git-changebar: fix compatibility with libgit2 0.28 API

[maxice8]

Namely rename the deprecated git_buf_free to git_buf_dispose and change
giterr calls to git_error.

[elextr]

This needs to select which name to use depending on the version of libgit the plugin is being built against.

[maxice8]

Ok they have been guarded under

#if LIBGIT2_VER_MAJOR == 0 && LIBGIT2_VER_MINOR >= 28
/* new api */
#else 
/* old api */
#endif 

[elextr]

According to the release notes API removals for 0.28, the old names are being kept for backward compatibility "for the foreseeable future", so this isn't really needed.

[b4n]

I didn't check the new API yet, but it's probably good to use it. But I'd rather see a backward compatibility chunk like there's around line 35, and change the code to use the new name.

[maxice8]

I removed the individual checks and added a block that defines git_buf_dispose to git_buf_free and git_error_last to giterr_last when libgit2 version is under 0.28.0

[b4n]

Otherwise looks good, although I didn't test it yet (will try to do tomorrow).

[b4n]

Works fine with 0.27 and 0.28, and indeed fixes support for a naive libgit2 build (which is not too nice on their part, but well… might actually be a bug).

[maxice8]

👍

[b4n]

and indeed fixes support for a naive libgit2 build (which is not too nice on their part, but well… might actually be a bug).

It is indeed a libgit2 bug and they are working on a fix.