fix edge case where changes are partially merged

__test__/create-or-update-branch.int.test.ts

@@ -657,6 +657,76 @@ describe('create-or-update-branch tests', () => {
     ).toBeTruthy()
   })
 
+  it('tests create, commit with partial changes on the base, and update', async () => {
+    // This is an edge case where the changes for a single commit are partially merged to the base
+
+    // Create tracked and untracked file changes
+    const changes = await createChanges()
+    const commitMessage = uuidv4()
+    const result = await createOrUpdateBranch(
+      git,
+      commitMessage,
+      '',
+      BRANCH,
+      REMOTE_NAME,
+      false,
+      ADD_PATHS_DEFAULT
+    )
+    await git.checkout(BRANCH)
+    expect(result.action).toEqual('created')
+    expect(await getFileContent(TRACKED_FILE)).toEqual(changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(changes.untracked)
+    expect(
+      await gitLogMatches([commitMessage, INIT_COMMIT_MESSAGE])
+    ).toBeTruthy()
+
+    // Push pull request branch to remote
+    await git.push([
+      '--force-with-lease',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${BRANCH}`
+    ])
+
+    await afterTest(false)
+    await beforeTest()
+
+    // Create a commit on the base with a partial merge of the changes
+    await createFile(TRACKED_FILE, changes.tracked)
+    const baseCommitMessage = uuidv4()
+    await git.exec(['add', '-A'])
+    await git.commit(['-m', baseCommitMessage])
+    await git.push([
+      '--force',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${DEFAULT_BRANCH}`
+    ])
+
+    // Create the same tracked and untracked file changes
+    const _changes = await createChanges(changes.tracked, changes.untracked)
+    const _commitMessage = uuidv4()
+    const _result = await createOrUpdateBranch(
+      git,
+      _commitMessage,
+      '',
+      BRANCH,
+      REMOTE_NAME,
+      false,
+      ADD_PATHS_DEFAULT
+    )
+    await git.checkout(BRANCH)
+    expect(_result.action).toEqual('updated')
+    expect(_result.hasDiffWithBase).toBeTruthy()
+    expect(await getFileContent(TRACKED_FILE)).toEqual(_changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(_changes.untracked)
+    expect(
+      await gitLogMatches([
+        _commitMessage,
+        baseCommitMessage,
+        INIT_COMMIT_MESSAGE
+      ])
+    ).toBeTruthy()
+  })
+
   it('tests create, squash merge, and update with identical changes', async () => {
     // Branches that have been squash merged appear to have a diff with the base due to
     // different commits for the same changes. To prevent creating pull requests
@@ -1679,6 +1749,81 @@ describe('create-or-update-branch tests', () => {
     ).toBeTruthy()
   })
 
+  it('tests create, commit with partial changes on the base, and update (WBNB)', async () => {
+    // This is an edge case where the changes for a single commit are partially merged to the base
+
+    // Set the working base to a branch that is not the pull request base
+    await git.checkout(NOT_BASE_BRANCH)
+
+    // Create tracked and untracked file changes
+    const changes = await createChanges()
+    const commitMessage = uuidv4()
+    const result = await createOrUpdateBranch(
+      git,
+      commitMessage,
+      BASE,
+      BRANCH,
+      REMOTE_NAME,
+      false,
+      ADD_PATHS_DEFAULT
+    )
+    await git.checkout(BRANCH)
+    expect(result.action).toEqual('created')
+    expect(await getFileContent(TRACKED_FILE)).toEqual(changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(changes.untracked)
+    expect(
+      await gitLogMatches([commitMessage, INIT_COMMIT_MESSAGE])
+    ).toBeTruthy()
+
+    // Push pull request branch to remote
+    await git.push([
+      '--force-with-lease',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${BRANCH}`
+    ])
+
+    await afterTest(false)
+    await beforeTest()
+
+    // Create a commit on the base with a partial merge of the changes
+    await createFile(TRACKED_FILE, changes.tracked)
+    const baseCommitMessage = uuidv4()
+    await git.exec(['add', '-A'])
+    await git.commit(['-m', baseCommitMessage])
+    await git.push([
+      '--force',
+      REMOTE_NAME,
+      `HEAD:refs/heads/${DEFAULT_BRANCH}`
+    ])
+
+    // Set the working base to a branch that is not the pull request base
+    await git.checkout(NOT_BASE_BRANCH)
+
+    // Create the same tracked and untracked file changes
+    const _changes = await createChanges(changes.tracked, changes.untracked)
+    const _commitMessage = uuidv4()
+    const _result = await createOrUpdateBranch(
+      git,
+      _commitMessage,
+      BASE,
+      BRANCH,
+      REMOTE_NAME,
+      false,
+      ADD_PATHS_DEFAULT
+    )
+    await git.checkout(BRANCH)
+    expect(_result.action).toEqual('updated')
+    expect(_result.hasDiffWithBase).toBeTruthy()
+    expect(await getFileContent(TRACKED_FILE)).toEqual(_changes.tracked)
+    expect(await getFileContent(UNTRACKED_FILE)).toEqual(_changes.untracked)
+    expect(
+      await gitLogMatches([
+        _commitMessage,
+        baseCommitMessage // fetch depth of base is 1
+      ])
+    ).toBeTruthy()
+  })
+
   it('tests create, squash merge, and update with identical changes (WBNB)', async () => {
     // Branches that have been squash merged appear to have a diff with the base due to
     // different commits for the same changes. To prevent creating pull requests

dist/index.js

@@ -133,6 +133,14 @@ function isEven(git, branch1, branch2) {
             !(yield isBehind(git, branch1, branch2)));
     });
 }
+// Return true if the specified number of commits on branch1 and branch2 have a diff
+function commitsHaveDiff(git, branch1, branch2, depth) {
+    return __awaiter(this, void 0, void 0, function* () {
+        const diff1 = (yield git.exec(['diff', '--stat', `${branch1}..${branch1}~${depth}`])).stdout.trim();
+        const diff2 = (yield git.exec(['diff', '--stat', `${branch2}..${branch2}~${depth}`])).stdout.trim();
+        return diff1 !== diff2;
+    });
+}
 function splitLines(multilineString) {
     return multilineString
         .split('\n')
@@ -241,20 +249,25 @@ function createOrUpdateBranch(git, commitMessage, base, branch, branchRemoteName
             yield git.checkout(branch);
             // Reset the branch if one of the following conditions is true.
             // - If the branch differs from the recreated temp branch.
+            // - If the number of commits ahead of the base branch differs between the branch and
+            //   temp branch. This catches a case where the base branch has been force pushed to
+            //   a new commit.
             // - If the recreated temp branch is not ahead of the base. This means there will be
             //   no pull request diff after the branch is reset. This will reset any undeleted
             //   branches after merging. In particular, it catches a case where the branch was
             //   squash merged but not deleted. We need to reset to make sure it doesn't appear
             //   to have a diff with the base due to different commits for the same changes.
-            // - If the number of commits ahead of the base branch differs between the branch and
+            // - If the diff of the commits ahead of the base branch differs between the branch and
-            //   temp branch. This catches a case where the base branch has been force pushed to
+            //   temp branch. This catches a case where changes have been partially merged to the
-            //   a new commit.
+            //   base. The overall diff is the same, but the branch needs to be rebased to show
+            //   the correct diff.
+            //
             // For changes on base this reset is equivalent to a rebase of the pull request branch.
             const branchCommitsAhead = yield commitsAhead(git, base, branch);
             if ((yield git.hasDiff([`${branch}..${tempBranch}`])) ||
                 branchCommitsAhead != tempBranchCommitsAhead ||
-                !(tempBranchCommitsAhead > 0) // !isAhead
+                !(tempBranchCommitsAhead > 0) || // !isAhead
-            ) {
+                (yield commitsHaveDiff(git, branch, tempBranch, tempBranchCommitsAhead))) {
                 core.info(`Resetting '${branch}'`);
                 // Alternatively, git switch -C branch tempBranch
                 yield git.checkout(branch, tempBranch);

src/create-or-update-branch.ts

@@ -124,6 +124,22 @@ async function isEven(
   )
 }
 
+// Return true if the specified number of commits on branch1 and branch2 have a diff
+async function commitsHaveDiff(
+  git: GitCommandManager,
+  branch1: string,
+  branch2: string,
+  depth: number
+): Promise<boolean> {
+  const diff1 = (
+    await git.exec(['diff', '--stat', `${branch1}..${branch1}~${depth}`])
+  ).stdout.trim()
+  const diff2 = (
+    await git.exec(['diff', '--stat', `${branch2}..${branch2}~${depth}`])
+  ).stdout.trim()
+  return diff1 !== diff2
+}
+
 function splitLines(multilineString: string): string[] {
   return multilineString
     .split('\n')
@@ -270,20 +286,26 @@ export async function createOrUpdateBranch(
 
     // Reset the branch if one of the following conditions is true.
     // - If the branch differs from the recreated temp branch.
+    // - If the number of commits ahead of the base branch differs between the branch and
+    //   temp branch. This catches a case where the base branch has been force pushed to
+    //   a new commit.
     // - If the recreated temp branch is not ahead of the base. This means there will be
     //   no pull request diff after the branch is reset. This will reset any undeleted
     //   branches after merging. In particular, it catches a case where the branch was
     //   squash merged but not deleted. We need to reset to make sure it doesn't appear
     //   to have a diff with the base due to different commits for the same changes.
-    // - If the number of commits ahead of the base branch differs between the branch and
+    // - If the diff of the commits ahead of the base branch differs between the branch and
-    //   temp branch. This catches a case where the base branch has been force pushed to
+    //   temp branch. This catches a case where changes have been partially merged to the
-    //   a new commit.
+    //   base. The overall diff is the same, but the branch needs to be rebased to show
+    //   the correct diff.
+    //
     // For changes on base this reset is equivalent to a rebase of the pull request branch.
     const branchCommitsAhead = await commitsAhead(git, base, branch)
     if (
       (await git.hasDiff([`${branch}..${tempBranch}`])) ||
       branchCommitsAhead != tempBranchCommitsAhead ||
-      !(tempBranchCommitsAhead > 0) // !isAhead
+      !(tempBranchCommitsAhead > 0) || // !isAhead
+      (await commitsHaveDiff(git, branch, tempBranch, tempBranchCommitsAhead))
     ) {
       core.info(`Resetting '${branch}'`)
       // Alternatively, git switch -C branch tempBranch