Added build option SONAME to control whether VERSION and SOVERSION were set for the git2 target, as some platforms require that this NOT be set.
immutable references and a pluggable ref database
Merge remote-tracking branch 'ethomson/immutable_refs' into development
refs: Dude, you're OUT.
optional tracing
Merge pull request #1403 from ethomson/tracing

Optional tracing back to consumers
Merge pull request #1399 from nathan-osman/development

Add SONAME build option to facilitate building for Android.
Use C99 stdio in mingw-w64

MinGW >= 3.14 does this automatically, but mingw-64 wants us to define
it.
diff: allow asking for diffs with no context

Previously, 0 meant default. This is problematic, as asking for 0
context lines is a valid thing to do.

Change GIT_DIFF_OPTIONS_INIT to default to three and stop treating 0
as a magic value. In case no options are provided, make sure the
options in the diff object default to 3.
Merge pull request #1175 from carlosmn/diff-0-ctx

Can't perform diff with no context lines
travis: join-less notifications