Won't this fail to find a system-provided libgit2?

Then https://github.com/libgit2/pygit2/blob/master/setup.py#L57 would fail too, no?

It seems Travis is having issues with this too. The problem I was trying to solve is that on OpenBSD git2.h lives in /usr/local/include . ffi.py would fail to find it unless I set LIBGIT2 for compilation and installation. I hoped there was a way it would either figure it out by itself or perhaps take it from setup.py ?

Travis is having issues because you've removed the logic that sets the correct path in case that there is a LIBGIT2 set. You're setting the list to empty instead of leaving that bit of logic as it was.

If your includes live under /usr/local/include, I don't see why you would need any changes. With the current code, in the absence of LIBGIT2, libgit2_path is set to /usr/local/ and that is joined with include, which would already be setting the default include path to /usr/local/include.

Sorry, I was looking at setup.py instead of ffi.py since they have essentially have the same block. Bu the solution would seem to be the same. If there is no path, set the path to /usr/local or /usr and the rest of the logic would work.

Here's the build log from my system: https://gist.github.com/jasperla/288c643e16fc3b59b64c (without the proposed patch)
Anything you spot wrong in there?

What I'm thinking of is something like this, which lets the current logic do the work and adds the fallback we have in setup.

diff --git a/pygit2/ffi.py b/pygit2/ffi.py
index 0dba2f3..b776dec 100644
--- a/pygit2/ffi.py
+++ b/pygit2/ffi.py
@@ -112,11 +112,13 @@ with codecs.open(decl_path, 'r', 'utf-8') as header:

 # if LIBGIT2 exists, set build and link against that version
 libgit2_path = getenv('LIBGIT2')
+if not libgit2_path:
+    libgit2_path = '/usr/local'
+
 include_dirs = []
 library_dirs = []
-if libgit2_path:
-    include_dirs = [path.join(libgit2_path, 'include')]
-    library_dirs = [path.join(libgit2_path, 'lib')]
+include_dirs = [path.join(libgit2_path, 'include')]
+library_dirs = [path.join(libgit2_path, 'lib')]

 C = ffi.verify("#include <git2.h>", libraries=["git2"],
                include_dirs=include_dirs, library_dirs=library_dirs)

That worked better indeed.