Cannot build new libgit2

[nacho]

/builddir/build/BUILD/libgit2-0.20.0/src/blame_git.c: In function 'diff_hunks':
/builddir/build/BUILD/libgit2-0.20.0/src/blame_git.c:351:7: error: 'xdemitconf_t' has no member named 'emit_func'

Although libgit2's xdiff copy seems to not have been updated since 2012...

[bochecha]

In libgit2's bundled xdiff, the xdemitconf_t structure is defined as follows:

typedef struct s_xdemitconf {
        long ctxlen;
        long interhunkctxlen;
        unsigned long flags;
        find_func_t find_func;
        void *find_func_priv;
        void (*emit_func)(void);
} xdemitconf_t;

In @spotrh's unbundled libxdiff, the same structure is defined as follows:

typedef struct s_xdemitconf {
        long ctxlen;
        long interhunkctxlen;
        unsigned long flags;
        find_func_t find_func;
        void *find_func_priv;
        xdl_emit_hunk_consume_func_t hunk_func;
} xdemitconf_t;

So the error message is actually quite obvious, spot's unbundled libxdiff indeed does not have an emit_func member.

[nacho]

Now the problem is, we are targetting mainly git and libgit2, we know libgit2 is using emit_func but what about git? is git using hunk_func? If yes we have a conflict here and either git or libgit2 should be fixed...

[nacho]

Adding @arrbee too

[bochecha]

In its xdiff/xdiff.h, Git 1.8.4.2 has:

typedef struct s_xdemitconf {
        long ctxlen;
        long interhunkctxlen;
        unsigned long flags;
        find_func_t find_func;
        void *find_func_priv;
        xdl_emit_hunk_consume_func_t hunk_func;
} xdemitconf_t;

So spot's libxdiff has the same thing as Git.

[arrbee]

I'm afraid I still don't see any evidence of activity on this project that motivates me to adopt it for libgit2 (as I have explained in libgit2/libgit2#1658 in more detail). I could be convinced to pull more recent code over from core Git because there is some evidence of active maintenance, but this project seems to be unmaintained (as I feared when this came up 6 months ago).

[nacho]

@arrbee pulling the latest stuff from git also works for us, since in that way we can always keep this up to date from the git's copy. Thoughts?

[arrbee]

@nacho I've started looking at pulling in the latest code from git.git directly into libgit2. There are significant API changes to accessing diff data so it is not a small change, but it does seem worthwhile to me. I will continue to work on it this week and see how much is actually involved.

By the way, I would still love it if this project became an effort to maintain and maybe even document an actual new libxdiff library. But I see that no xdiff related commits from git.git have ever been pulled into this repo since the initial creation, even though some of those are now more than 6 months old. Ah well.

[nacho]

@arrbee what about making this a submodule of libgit2? the idea would be to be pushing all the latest git stuff here and use it in libgit2. This way:

1. libgit2 would decide which commit to use
2. distributions would have a single place where to fetch the module

See also that would mean making you part of the maintainers of this module

[bochecha]

Seconding @nacho's submodule suggestion.

Also, I've just opened #3 which updates to the latest xdiff code in Git, as @arrbee correctly found that this repository was out of date.

[nacho]

@spotrh any comments on this?

[spotrh]

I have just merged bochecha's changes to sync with the latest code in git. I haven't had anywhere near as much time as I would have liked to push this, but I greatly appreciate the help.

[nacho]

@spotrh what about making a new release with these changes so we can create a new package for libxdiff and patch libgit2 to use it?