feat(api): add q parameter to list branches API for server-side filtering (#37982)

The GET /repos/{owner}/{repo}/branches endpoint currently has no way to
filter branches by name server-side, forcing API consumers to paginate
through all branches and filter client-side.

The UI already supports branch search (added in
[#27055](https://github.com/go-gitea/gitea/pull/27055)). The underlying
DB layer has a Keyword field on FindBranchOptions in
models/git/branch_list.go that does a LIKE %keyword% SQL filter, it just
wasn't wired up to the API handler.

This PR exposes a ?q= query parameter on the endpoint that maps to
FindBranchOptions.Keyword.

Example:

```GET /repos/owner/repo/branches?q=feature ```
Closes #37981

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/api/v1/repo/branch.go

@@ -306,6 +306,10 @@ func ListBranches(ctx *context.APIContext) {
 	//   in: query
 	//   description: page size of results
 	//   type: integer
+	// - name: q
+	//   in: query
+	//   description: branch name substring to filter by
+	//   type: string
 	// responses:
 	//   "200":
 	//     "$ref": "#/responses/BranchList"
@@ -314,6 +318,7 @@ func ListBranches(ctx *context.APIContext) {
 	var apiBranches []*api.Branch
 
 	listOptions := utils.GetListOptions(ctx)
+	keyword := ctx.FormString("q")
 
 	if !ctx.Repo.Repository.IsEmpty {
 		if ctx.Repo.GitRepo == nil {
@@ -325,6 +330,7 @@ func ListBranches(ctx *context.APIContext) {
 			ListOptions:     listOptions,
 			RepoID:          ctx.Repo.Repository.ID,
 			IsDeletedBranch: optional.Some(false),
+			Keyword:         keyword,
 		}
 		var err error
 		totalNumOfBranches, err = db.Count[git_model.Branch](ctx, branchOpts)

templates/swagger/v1_json.tmpl

@@ -7158,6 +7158,12 @@
             "description": "page size of results",
             "name": "limit",
             "in": "query"
+          },
+          {
+            "type": "string",
+            "description": "branch name substring to filter by",
+            "name": "q",
+            "in": "query"
           }
         ],
         "responses": {

templates/swagger/v1_openapi3_json.tmpl

@@ -18224,6 +18224,14 @@
             "schema": {
               "type": "integer"
             }
+          },
+          {
+            "description": "branch name substring to filter by",
+            "in": "query",
+            "name": "q",
+            "schema": {
+              "type": "string"
+            }
           }
         ],
         "responses": {

tests/integration/api_repo_branch_test.go

@@ -128,3 +128,20 @@ func TestAPIRepoBranchesMirror(t *testing.T) {
 	assert.NoError(t, err)
 	assert.JSONEq(t, "{\"message\":\"Git Repository is a mirror.\",\"url\":\""+setting.AppURL+"api/swagger\"}", string(bs))
 }
+
+func TestAPIRepoBranchesSearch(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	token := getUserToken(t, "user1", auth_model.AccessTokenScopeWriteRepository)
+
+	// "test" matches "test_branch" but not "master"
+	resp := MakeRequest(t, NewRequestf(t, "GET", "/api/v1/repos/org3/repo3/branches?q=test").AddTokenAuth(token), http.StatusOK)
+	branches := DecodeJSON(t, resp, []api.Branch{})
+	assert.Len(t, branches, 1)
+	assert.Equal(t, "test_branch", branches[0].Name)
+
+	// no match returns empty list
+	resp = MakeRequest(t, NewRequestf(t, "GET", "/api/v1/repos/org3/repo3/branches?q=doesnotexist").AddTokenAuth(token), http.StatusOK)
+	branches = DecodeJSON(t, resp, []api.Branch{})
+	assert.Empty(t, branches)
+}

tests/integration/integration_test.go

@@ -323,6 +323,10 @@ func logUnexpectedResponse(t testing.TB, recorder *httptest.ResponseRecorder) {
 	}
 }
 
+// DecodeJSON decodes then response as JSON into typed variable and return it
+// HINT: don't use it on existing variable (reuse existing variable):
+// if the existing var already contains some values but the new input doesn't, then it leads to wrong test result in edge cases.
+// For slice decoding, use: v := DecodeJSON(t, resp, []T{})
 func DecodeJSON[T any](t testing.TB, resp *httptest.ResponseRecorder, v T) (ret T) {
 	t.Helper()