Fix IDE commit to use start_ref59023-fix-web-ide-creating-branches-off-new-commits

**Why?**
The branch HEAD could be changed since the
IDE was opened. This leads to user's unintentionally
creating commits that overwrite other changes.

https://gitlab.com/gitlab-org/gitlab-ce/issues/59023

7 files changed, 92 insertions, 10 deletions

diff --git a/app/assets/javascripts/ide/services/index.js b/app/assets/javascripts/ide/services/index.js
index ba33b6826d6..840761f68db 100644
--- a/app/assets/javascripts/ide/services/index.js
+++ b/app/assets/javascripts/ide/services/index.js
@@ -56,7 +56,13 @@ export default {
     return Api.branchSingle(projectId, currentBranchId);
   },
   commit(projectId, payload) {
-    return Api.commitMultiple(projectId, payload);
+    // Currently the `commit` endpoint does not support `start_sha` so we
+    // have to make the request in the FE. This is not ideal and will be
+    // resolved soon. https://gitlab.com/gitlab-org/gitlab-ce/issues/59023
+    const { branch, start_sha: ref } = payload;
+    const branchPromise = ref ? Api.createBranch(projectId, { ref, branch }) : Promise.resolve();
+
+    return branchPromise.then(() => Api.commitMultiple(projectId, payload));
   },
   getFiles(projectUrl, branchId) {
     const url = `${projectUrl}/files/${branchId}`;
diff --git a/app/assets/javascripts/ide/stores/modules/commit/actions.js b/app/assets/javascripts/ide/stores/modules/commit/actions.js
index 51062f092ad..ff1255ce749 100644
--- a/app/assets/javascripts/ide/stores/modules/commit/actions.js
+++ b/app/assets/javascripts/ide/stores/modules/commit/actions.js
@@ -142,6 +142,7 @@ export const commitChanges = ({ commit, state, getters, dispatch, rootState, roo
         getters,
         state,
         rootState,
+        rootGetters,
       });
 
       return service.commit(rootState.currentProjectId, payload);
diff --git a/app/assets/javascripts/ide/stores/utils.js b/app/assets/javascripts/ide/stores/utils.js
index bcc9ca60d9b..4e7a8765abe 100644
--- a/app/assets/javascripts/ide/stores/utils.js
+++ b/app/assets/javascripts/ide/stores/utils.js
@@ -135,7 +135,14 @@ export const getCommitFiles = stagedFiles =>
     });
   }, []);
 
-export const createCommitPayload = ({ branch, getters, newBranch, state, rootState }) => ({
+export const createCommitPayload = ({
+  branch,
+  getters,
+  newBranch,
+  state,
+  rootState,
+  rootGetters,
+}) => ({
   branch,
   commit_message: state.commitMessage || getters.preBuiltCommitMessage,
   actions: getCommitFiles(rootState.stagedFiles).map(f => ({
@@ -146,7 +153,7 @@ export const createCommitPayload = ({ branch, getters, newBranch, state, rootSta
     encoding: f.base64 ? 'base64' : 'text',
     last_commit_id: newBranch || f.deleted || f.prevPath ? undefined : f.lastCommitSha,
   })),
-  start_branch: newBranch ? rootState.currentBranchId : undefined,
+  start_sha: newBranch ? rootGetters.lastCommit.short_id : undefined,
 });
 
 export const createNewMergeRequestUrl = (projectUrl, source, target) =>
diff --git a/changelogs/unreleased/59023-fix-web-ide-creating-branches-off-new-commits.yml b/changelogs/unreleased/59023-fix-web-ide-creating-branches-off-new-commits.yml
new file mode 100644
index 00000000000..f7e0ee333aa
--- /dev/null
+++ b/changelogs/unreleased/59023-fix-web-ide-creating-branches-off-new-commits.yml
@@ -0,0 +1,5 @@
+---
+title: Fix IDE commit using latest ref in branch and overriding contents
+merge_request: 29769
+author:
+type: fixed
diff --git a/spec/frontend/ide/services/index_spec.js b/spec/frontend/ide/services/index_spec.js
new file mode 100644
index 00000000000..499fa8fc012
--- /dev/null
+++ b/spec/frontend/ide/services/index_spec.js
@@ -0,0 +1,55 @@
+import services from '~/ide/services';
+import Api from '~/api';
+
+jest.mock('~/api');
+
+const TEST_PROJECT_ID = 'alice/wonderland';
+const TEST_BRANCH = 'master-patch-123';
+const TEST_COMMIT_SHA = '123456789';
+
+describe('IDE services', () => {
+  describe('commit', () => {
+    let payload;
+
+    beforeEach(() => {
+      payload = {
+        branch: TEST_BRANCH,
+        commit_message: 'Hello world',
+        actions: [],
+        start_sha: undefined,
+      };
+
+      Api.createBranch.mockReturnValue(Promise.resolve());
+      Api.commitMultiple.mockReturnValue(Promise.resolve());
+    });
+
+    describe.each`
+      startSha           | shouldCreateBranch
+      ${undefined}       | ${false}
+      ${TEST_COMMIT_SHA} | ${true}
+    `('when start_sha is $startSha', ({ startSha, shouldCreateBranch }) => {
+      beforeEach(() => {
+        payload.start_sha = startSha;
+
+        return services.commit(TEST_PROJECT_ID, payload);
+      });
+
+      if (shouldCreateBranch) {
+        it('should create branch', () => {
+          expect(Api.createBranch).toHaveBeenCalledWith(TEST_PROJECT_ID, {
+            ref: TEST_COMMIT_SHA,
+            branch: TEST_BRANCH,
+          });
+        });
+      } else {
+        it('should not create branch', () => {
+          expect(Api.createBranch).not.toHaveBeenCalled();
+        });
+      }
+
+      it('should commit', () => {
+        expect(Api.commitMultiple).toHaveBeenCalledWith(TEST_PROJECT_ID, payload);
+      });
+    });
+  });
+});
diff --git a/spec/javascripts/ide/stores/modules/commit/actions_spec.js b/spec/javascripts/ide/stores/modules/commit/actions_spec.js
index 5f7272311c8..8a3c132972e 100644
--- a/spec/javascripts/ide/stores/modules/commit/actions_spec.js
+++ b/spec/javascripts/ide/stores/modules/commit/actions_spec.js
@@ -6,9 +6,11 @@ import eventHub from '~/ide/eventhub';
 import consts from '~/ide/stores/modules/commit/constants';
 import * as mutationTypes from '~/ide/stores/modules/commit/mutation_types';
 import * as actions from '~/ide/stores/modules/commit/actions';
-import testAction from '../../../../helpers/vuex_action_helper';
 import { commitActionTypes } from '~/ide/constants';
 import { resetStore, file } from 'spec/ide/helpers';
+import testAction from '../../../../helpers/vuex_action_helper';
+
+const TEST_COMMIT_SHA = '123456789';
 
 describe('IDE commit module actions', () => {
   beforeEach(() => {
@@ -139,6 +141,9 @@ describe('IDE commit module actions', () => {
         branches: {
           master: {
             workingReference: '',
+            commit: {
+              short_id: TEST_COMMIT_SHA,
+            },
           },
         },
       };
@@ -239,6 +244,9 @@ describe('IDE commit module actions', () => {
         branches: {
           master: {
             workingReference: '1',
+            commit: {
+              short_id: TEST_COMMIT_SHA,
+            },
           },
         },
       };
@@ -247,7 +255,7 @@ describe('IDE commit module actions', () => {
         ...file('changed'),
         type: 'blob',
         active: true,
-        lastCommitSha: '123456789',
+        lastCommitSha: TEST_COMMIT_SHA,
       };
       store.state.stagedFiles.push(f);
       store.state.changedFiles = [
@@ -307,7 +315,7 @@ describe('IDE commit module actions', () => {
                   previous_path: undefined,
                 },
               ],
-              start_branch: 'master',
+              start_sha: TEST_COMMIT_SHA,
             });
 
             done();
@@ -330,11 +338,11 @@ describe('IDE commit module actions', () => {
                   file_path: jasmine.anything(),
                   content: undefined,
                   encoding: jasmine.anything(),
-                  last_commit_id: '123456789',
+                  last_commit_id: TEST_COMMIT_SHA,
                   previous_path: undefined,
                 },
               ],
-              start_branch: undefined,
+              start_sha: undefined,
             });
 
             done();
diff --git a/spec/javascripts/ide/stores/utils_spec.js b/spec/javascripts/ide/stores/utils_spec.js
index debe1c4acee..e3bf6d40245 100644
--- a/spec/javascripts/ide/stores/utils_spec.js
+++ b/spec/javascripts/ide/stores/utils_spec.js
@@ -132,7 +132,7 @@ describe('Multi-file store utils', () => {
             previous_path: undefined,
           },
         ],
-        start_branch: undefined,
+        start_sha: undefined,
       });
     });
 
@@ -187,7 +187,7 @@ describe('Multi-file store utils', () => {
             previous_path: undefined,
           },
         ],
-        start_branch: undefined,
+        start_sha: undefined,
       });
     });
   });