fix: split refspecs on the last colon, like Git does

gix-refspec/src/parse.rs

@@ -75,7 +75,10 @@ pub(crate) mod function {
             }
         };
 
-        let (mut src, dst) = match spec.find_byte(b':') {
+        // Split on the last colon like `strrchr()` in Git's `parse_refspec()` does, so that a
+        // push source may itself contain one - `:/message` and `<rev>:<path>` are both valid
+        // revisions. With a single colon this is the same position as the first one.
+        let (mut src, dst) = match spec.rfind_byte(b':') {
             Some(pos) => {
                 if mode == Mode::Negative {
                     return Err(Error::NegativeWithDestination);

gix-refspec/tests/fixtures/parse_baseline.sh

@@ -40,6 +40,11 @@ baseline push '^'
 
 baseline fetch '^refs/heads/qa/*/*'
 baseline push '^refs/heads/qa/*/*'
+
+# a fetch source is a ref name, so it can't hold the colon that a push source may
+baseline fetch 'a:b:c'
+baseline fetch ':/message:refs/heads/x'
+
 baseline push 'main~1'
 baseline fetch 'main~1'
 baseline push 'main~1:other~1'
@@ -92,6 +97,12 @@ baseline fetch 'refs/heads/main:refs/remotes/frotz/xyzzy'
 baseline push 'main~1:refs/remotes/frotz/backup'
 baseline push 'HEAD~4:refs/remotes/frotz/new'
 
+# Git splits on the last colon, so a push source may contain one itself
+baseline push 'a:b:c'
+baseline push 'a:b:c:d'
+baseline push ':/message:refs/heads/x'
+baseline push 'HEAD:path:refs/heads/x'
+
 baseline push 'HEAD'
 baseline fetch 'HEAD'
 baseline push '@'