Merge branch 'jk/complete-commit-c' into maint

* jk/complete-commit-c:
  completion: complete refs for "git commit -c"
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 0b77eb1..a4c48e1 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -971,6 +971,13 @@
 {
 	__git_has_doubledash && return
 
+	case "$prev" in
+	-c|-C)
+		__gitcomp_nl "$(__git_refs)" "" "${cur}"
+		return
+		;;
+	esac
+
 	case "$cur" in
 	--cleanup=*)
 		__gitcomp "default strip verbatim whitespace