supergit: implementing simple file-history search

This is done by stepping through a branch iterator to diff commits to
see where they changed.  This is somewhat computationally intensive,
and also doesn't work well yet because iterator stepping is done
internally and there is no API to extend iterators before they are
run.  That means that histories can only be read from first-parent
iterators.

Ideally we would do two things here:

1. build an API to let iterators extend themselves, either breadth
   first, or depth first.  But maybe that would be too much
   complexity for the iterator module?

2. figure out a better way to get the history of a file.  At the
   moment we are stepping through commits and diffing them with
   parents to find the set of changed paths.  I don't _think_ there is
   a way to simply compare refs, but maybe there is.

1 files changed, 10 insertions, 0 deletions

diff --git a/apps/servers/octopus/supergit/src/branch.rs b/apps/servers/octopus/supergit/src/branch.rs
index 432227900247..3261d23b9177 100644
--- a/apps/servers/octopus/supergit/src/branch.rs
+++ b/apps/servers/octopus/supergit/src/branch.rs
@@ -248,4 +248,14 @@ impl BranchCommit {
         }
         .clone()
     }
+
+    /// Get the underlying commit, regardless of type
+    pub fn commit(&self) -> &Commit {
+        use BranchCommit::*;
+        match self {
+            Commit(ref c) => c,
+            Merge(ref c, _) => c,
+            Octopus(ref c, _) => c,
+        }
+    }
 }