main::update(): Change HEAD branch if default branch changed

If the default branch on GitHub changed, change the local mirror's HEAD
to match the new default.

Need to store the default branch in the database now so we can find out
whether it changed.

1 files changed, 26 insertions, 3 deletions

diff --git a/src/git.rs b/src/git.rs
index 753137c..ccc0922 100644
--- a/src/git.rs
+++ b/src/git.rs
@@ -76,9 +76,7 @@ pub fn mirror<P: AsRef<Path>>(
     remote.fetch(&refspecs, None, None)?;
 
     if default_branch != "master" {
-        repo.set_head(
-            &format!("refs/heads/{}", default_branch),
-        )?;
+        repo_change_current_branch(&repo, default_branch)?;
     }
 
     Ok(())
@@ -133,3 +131,28 @@ pub fn update_description<P: AsRef<Path>>(
 
     Ok(())
 }
+
+/// Change the current branch of the repository at `repo_path` to
+/// `default_branch`.
+pub fn change_current_branch<P: AsRef<Path>>(
+    repo_path: P,
+    default_branch: &str,
+) -> Result<(), Error> {
+    let repo = git2::Repository::open_bare(repo_path)?;
+
+    Ok(
+        repo_change_current_branch(&repo, default_branch)?
+    )
+}
+
+/// Change `repo`'s current branch to `default_branch`.
+fn repo_change_current_branch(
+    repo: &git2::Repository,
+    default_branch: &str,
+) -> Result<(), Error> {
+    Ok(
+        repo.set_head(
+            &format!("refs/heads/{}", default_branch),
+        )?
+    )
+}