Make reclone with implicit branch update branch in .gitrepo correctly

.travis.yml

@@ -4,18 +4,9 @@ sudo: false
 # Want 'bash' but 'c' works:
 language: c
 
-branches:
-  only:
-  - master
-  - /^release\//
-
 script:
-- git checkout $(
-    git branch --contains HEAD
-        | cut -c3-
-        | grep -E '^(master$|release)'
-        | head -1
-  )
+# NOTE: we have to make sure we're on a branch (rather than on a detached HEAD) because tests rely on it.
+- git checkout -b travis-ci-dummy-branch-name
 - GIT_COMMITTER_NAME=Bob
   [email protected]
   GIT_AUTHOR_NAME='Bob Blob'

lib/git-subrepo

@@ -478,6 +478,13 @@ subrepo:clone() {
     fi
     o "Remove the old subdir."
     RUN git rm -r -- "$subdir"
+
+    if [[ -z $override_branch ]]; then
+      o "Determine the upstream head branch."
+      get-upstream-head-branch
+      subrepo_branch="$output"
+      override_branch="$output" # Force update of the branch in .gitrepo
+    fi
   else
     assert-subdir-empty
     if [[ -z $subrepo_branch ]]; then

test/reclone.t

@@ -16,6 +16,7 @@ clone-foo-and-bar
 test-exists \
   "$OWNER/foo/bar/bard/"
 
+# Test that reclone is not done if not needed.
 export XYZ=1
 is "$(
   cd $OWNER/foo
@@ -24,19 +25,25 @@ is "$(
   "Subrepo 'bar' is up to date." \
   "No reclone if same commit"
 
+# Test that reclone of a different ref works.
 (
   cd $OWNER/foo
   git subrepo --quiet clone --force ../../../$UPSTREAM/bar --branch=refs/tags/A
 )
 
+is "$(git -C $OWNER/foo subrepo config bar branch)" \
+  "Subrepo 'bar' option 'branch' has value 'refs/tags/A'."
 test-exists \
   "!$OWNER/foo/bar/bard/"
 
+# Test that reclone back to (implicit) master works.
 (
   cd $OWNER/foo
-  git subrepo --quiet clone -f ../../../$UPSTREAM/bar --branch=master
+  git subrepo --quiet clone -f ../../../$UPSTREAM/bar
 )
 
+is "$(git -C $OWNER/foo subrepo config bar branch)" \
+  "Subrepo 'bar' option 'branch' has value 'master'."
 test-exists \
   "$OWNER/foo/bar/bard/"