commit - 3f9de99f9b4d3da34a06dfce54134ff891684df9
commit + 30837e32b8c05d75e429f5587a658d6df7ddfda8
blob - 59507d1863a1ad983bf5f3e0811d54e3c511f8f5
blob + 6bfe01e0cf9d122e717e568966eb3ac3f555b1f9
--- got/got.1
+++ got/got.1
@@ -143,7 +143,8 @@ reference will be used.
 .It Fl c Ar commit
 Check out files from the specified
 .Ar commit .
-The expected argument is a commit ID SHA1 hash.
+The expected argument is a commit ID SHA1 hash or an existing reference
+which will be resolved to a commit ID.
 An abbreviated hash argument will be expanded to a full SHA1 hash
 automatically, provided the abbreviation is unique.
 If this option is not specified, the most recent commit on the selected
@@ -201,7 +202,8 @@ This option requires that all paths in the work tree a
 .It Fl c Ar commit
 Update the work tree to the specified
 .Ar commit .
-The expected argument is a commit ID SHA1 hash.
+The expected argument is a commit ID SHA1 hash or an existing reference
+which will be resolved to a commit ID.
 An abbreviated hash argument will be expanded to a full SHA1 hash
 automatically, provided the abbreviation is unique.
 If this option is not specified, the most recent commit on the work tree's
@@ -243,7 +245,8 @@ are as follows:
 .It Fl c Ar commit
 Start traversing history at the specified
 .Ar commit .
-The expected argument is the name of a branch or a commit ID SHA1 hash.
+The expected argument is a commit ID SHA1 hash or an existing reference
+which will be resolved to a commit ID.
 An abbreviated hash argument will be expanded to a full SHA1 hash
 automatically, provided the abbreviation is unique.
 If this option is not specified, default to the work tree's current branch
@@ -307,7 +310,8 @@ are as follows:
 .It Fl c Ar commit
 Start traversing history at the specified
 .Ar commit .
-The expected argument is the name of a branch or a commit ID SHA1 hash.
+The expected argument is a commit ID SHA1 hash or an existing reference
+which will be resolved to a commit ID.
 An abbreviated hash argument will be expanded to a full SHA1 hash
 automatically, provided the abbreviation is unique.
 .It Fl r Ar repository-path
@@ -341,7 +345,8 @@ are as follows:
 .It Fl c Ar commit
 List files and directories as they appear in the specified
 .Ar commit .
-The expected argument is the name of a branch or a commit ID SHA1 hash.
+The expected argument is a commit ID SHA1 hash or an existing reference
+which will be resolved to a commit ID.
 An abbreviated hash argument will be expanded to a full SHA1 hash
 automatically, provided the abbreviation is unique.
 .It Fl r Ar repository-path
blob - b5341e17acdb3b81c77d3cce58a2ab5c6c010c6c
blob + a16ed7b70ecc012e088c02a4df0d6f13e4e268a6
--- got/got.c
+++ got/got.c
@@ -900,10 +900,19 @@ cmd_checkout(int argc, char *argv[])
 	}
 
 	if (commit_id_str) {
-		struct got_object_id *commit_id;
-		error = got_repo_match_object_id_prefix(&commit_id,
-		    commit_id_str, GOT_OBJ_TYPE_COMMIT, repo);
-		if (error != NULL)
+		struct got_object_id *commit_id = NULL;
+		struct got_reference *ref;
+		error = got_ref_open(&ref, repo, commit_id_str, 0);
+		if (error == NULL) {
+			error = got_ref_resolve(&commit_id, repo, ref);
+			got_ref_close(ref);
+		} else {
+			if (error->code != GOT_ERR_NOT_REF)
+				goto done;
+			error = got_repo_match_object_id_prefix(&commit_id,
+			    commit_id_str, GOT_OBJ_TYPE_COMMIT, repo);
+		}
+		if (error)
 			goto done;
 		error = check_linear_ancestry(commit_id,
 		    got_worktree_get_base_commit_id(worktree), repo);
@@ -1108,9 +1117,19 @@ cmd_update(int argc, char *argv[])
 		if (error != NULL)
 			goto done;
 	} else {
-		error = got_repo_match_object_id_prefix(&commit_id,
-		    commit_id_str, GOT_OBJ_TYPE_COMMIT, repo);
-		if (error != NULL)
+		struct got_reference *ref;
+		error = got_ref_open(&ref, repo, commit_id_str, 0);
+		if (error == NULL) {
+			error = got_ref_resolve(&commit_id, repo, ref);
+			got_ref_close(ref);
+		}
+		else {
+			if (error->code != GOT_ERR_NOT_REF)
+				goto done;
+			error = got_repo_match_object_id_prefix(&commit_id,
+			    commit_id_str, GOT_OBJ_TYPE_COMMIT, repo);
+		}
+		if (error)
 			goto done;
 		free(commit_id_str);
 		error = got_object_id_str(&commit_id_str, commit_id);
@@ -2015,9 +2034,18 @@ cmd_blame(int argc, char *argv[])
 		if (error != NULL)
 			goto done;
 	} else {
-		error = got_repo_match_object_id_prefix(&commit_id,
-		    commit_id_str, GOT_OBJ_TYPE_COMMIT, repo);
-		if (error != NULL)
+		struct got_reference *ref;
+		error = got_ref_open(&ref, repo, commit_id_str, 0);
+		if (error == NULL) {
+			error = got_ref_resolve(&commit_id, repo, ref);
+			got_ref_close(ref);
+		} else {
+			if (error->code != GOT_ERR_NOT_REF)
+				goto done;
+			error = got_repo_match_object_id_prefix(&commit_id,
+			    commit_id_str, GOT_OBJ_TYPE_COMMIT, repo);
+		}
+		if (error)
 			goto done;
 	}
 
@@ -2247,9 +2275,18 @@ cmd_tree(int argc, char *argv[])
 		if (error != NULL)
 			goto done;
 	} else {
-		error = got_repo_match_object_id_prefix(&commit_id,
-		    commit_id_str, GOT_OBJ_TYPE_COMMIT, repo);
-		if (error != NULL)
+		struct got_reference *ref;
+		error = got_ref_open(&ref, repo, commit_id_str, 0);
+		if (error == NULL) {
+			error = got_ref_resolve(&commit_id, repo, ref);
+			got_ref_close(ref);
+		} else {
+			if (error->code != GOT_ERR_NOT_REF)
+				goto done;
+			error = got_repo_match_object_id_prefix(&commit_id,
+			    commit_id_str, GOT_OBJ_TYPE_COMMIT, repo);
+		}
+		if (error)
 			goto done;
 	}