From cb61409d88d8175e42e129042f05b58baf0252f8 Mon Sep 17 00:00:00 2001
From: keerthigkaarthik <120106412+keerthigkaarthik@users.noreply.github.com>
Date: Fri, 14 Nov 2025 10:08:15 +0100
Subject: [PATCH 1/6] Add branch forward exercise

---
 branch_forward/.gitmastery-exercise.json      | 17 +++++
 branch_forward/README.md                      | 26 ++++++++
 branch_forward/__init__.py                    |  0
 branch_forward/download.py                    | 63 +++++++++++++++++++
 branch_forward/tests/__init__.py              |  0
 branch_forward/tests/specs/base.yml           | 42 +++++++++++++
 .../tests/specs/merge_with_sally_no_ff.yml    | 43 +++++++++++++
 branch_forward/tests/specs/no_merges.yml      | 41 ++++++++++++
 .../tests/specs/other_branch_ff.yml           | 53 ++++++++++++++++
 .../tests/specs/other_branch_non_ff.yml       | 43 +++++++++++++
 branch_forward/tests/test_verify.py           | 52 +++++++++++++++
 branch_forward/verify.py                      | 42 +++++++++++++
 12 files changed, 422 insertions(+)
 create mode 100644 branch_forward/.gitmastery-exercise.json
 create mode 100644 branch_forward/README.md
 create mode 100644 branch_forward/__init__.py
 create mode 100644 branch_forward/download.py
 create mode 100644 branch_forward/tests/__init__.py
 create mode 100644 branch_forward/tests/specs/base.yml
 create mode 100644 branch_forward/tests/specs/merge_with_sally_no_ff.yml
 create mode 100644 branch_forward/tests/specs/no_merges.yml
 create mode 100644 branch_forward/tests/specs/other_branch_ff.yml
 create mode 100644 branch_forward/tests/specs/other_branch_non_ff.yml
 create mode 100644 branch_forward/tests/test_verify.py
 create mode 100644 branch_forward/verify.py

diff --git a/branch_forward/.gitmastery-exercise.json b/branch_forward/.gitmastery-exercise.json
new file mode 100644
index 0000000..63acafd
--- /dev/null
+++ b/branch_forward/.gitmastery-exercise.json
@@ -0,0 +1,17 @@
+{
+  "exercise_name": "branch-forward",
+  "tags": [
+    "git-branch",
+    "git-merge"
+  ],
+  "requires_git": true,
+  "requires_github": false,
+  "base_files": {},
+  "exercise_repo": {
+    "repo_type": "local",
+    "repo_name": "love-story",
+    "repo_title": null,
+    "create_fork": null,
+    "init": true
+  }
+}
\ No newline at end of file
diff --git a/branch_forward/README.md b/branch_forward/README.md
new file mode 100644
index 0000000..af774d7
--- /dev/null
+++ b/branch_forward/README.md
@@ -0,0 +1,26 @@
+# branch-forward
+
+You are outlining a story and experimenting with different plotlines. Each version lives on its own branch, and you now need to fold the right storyline back into `main` without cluttering the history.
+
+## Learning objectives
+
+- Identify when a branch can be fast-forward merged
+- Use fast-forward merges to keep the commit graph linear
+- [Fast-forward merges](https://nus-cs2103-ay2526s1.github.io/website/book/gitAndGithub/merge/index.html)
+
+## Task
+
+1. Review the `with-sally` and `with-ginny` branches.
+2. Merge only the branch(es) that can be fast-forwarded into `main`.
+3. Leave other branches (if any) unmerged.
+
+## Hints
+
+
+<details>
+
+<summary>Hint 1</summary>
+
+Ensure you have switched to the destination branch before initiating the merge.
+
+</details>
\ No newline at end of file
diff --git a/branch_forward/__init__.py b/branch_forward/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/branch_forward/download.py b/branch_forward/download.py
new file mode 100644
index 0000000..1eff523
--- /dev/null
+++ b/branch_forward/download.py
@@ -0,0 +1,63 @@
+from exercise_utils.file import append_to_file
+from exercise_utils.git import add, checkout, commit
+
+
+def setup(verbose: bool = False):
+    append_to_file(
+        "story.txt",
+        """
+        Harry was single.
+        """,
+    )
+    add(["story.txt"], verbose)
+    commit("Introduce Harry", verbose)
+
+    append_to_file(
+        "story.txt",
+        """
+        Harry did not have a family.
+        """,
+    )
+    add(["story.txt"], verbose)
+    commit("Add about family", verbose)
+
+    checkout("with-ginny", True, verbose)
+    append_to_file(
+        "story.txt",
+        """
+        Then he met Ginny.
+        """,
+    )
+    add(["story.txt"], verbose)
+    commit("Add about Ginny", verbose)
+
+    checkout("main", False, verbose)
+    append_to_file(
+        "cast.txt",
+        """
+        Harry
+        """,
+    )
+    add(["cast.txt"], verbose)
+    commit("Add cast.txt", verbose)
+
+    checkout("with-sally", True, verbose)
+    append_to_file(
+        "story.txt",
+        """
+        Then he met Sally
+        """,
+    )
+    add(["story.txt"], verbose)
+    commit("Mention Sally", verbose)
+
+    checkout("with-ginny", False, verbose)
+    append_to_file(
+        "story.txt",
+        """
+        Ginny was single too
+        """,
+    )
+    add(["story.txt"], verbose)
+    commit("Mention Ginny is single", verbose)
+    
diff --git a/branch_forward/tests/__init__.py b/branch_forward/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/branch_forward/tests/specs/base.yml b/branch_forward/tests/specs/base.yml
new file mode 100644
index 0000000..99af44c
--- /dev/null
+++ b/branch_forward/tests/specs/base.yml
@@ -0,0 +1,42 @@
+initialization:
+  steps:
+    - type: commit
+      empty: true
+      message: Introduce Harry
+      id: start
+    - type: commit
+      empty: true
+      message: Add about family
+
+    - type: branch
+      branch-name: with-ginny
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Add about Ginny
+
+    - type: checkout
+      branch-name: main
+    - type: commit
+      empty: true
+      message: Add cast.txt
+
+    - type: branch
+      branch-name: with-sally
+    - type: checkout
+      branch-name: with-sally
+    - type: commit
+      empty: true
+      message: Mention Sally
+
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Mention Ginny is single
+
+    - type: checkout
+      branch-name: main
+    - type: merge
+      branch-name: with-sally
diff --git a/branch_forward/tests/specs/merge_with_sally_no_ff.yml b/branch_forward/tests/specs/merge_with_sally_no_ff.yml
new file mode 100644
index 0000000..1b76e03
--- /dev/null
+++ b/branch_forward/tests/specs/merge_with_sally_no_ff.yml
@@ -0,0 +1,43 @@
+initialization:
+  steps:
+    - type: commit
+      empty: true
+      message: Introduce Harry
+      id: start
+    - type: commit
+      empty: true
+      message: Add about family
+
+    - type: branch
+      branch-name: with-ginny
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Add about Ginny
+
+    - type: checkout
+      branch-name: main
+    - type: commit
+      empty: true
+      message: Add cast.txt
+
+    - type: branch
+      branch-name: with-sally
+    - type: checkout
+      branch-name: with-sally
+    - type: commit
+      empty: true
+      message: Mention Sally
+
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Mention Ginny is single
+
+    - type: checkout
+      branch-name: main
+    - type: merge
+      branch-name: with-sally
+      no-ff: true
diff --git a/branch_forward/tests/specs/no_merges.yml b/branch_forward/tests/specs/no_merges.yml
new file mode 100644
index 0000000..2d0ece0
--- /dev/null
+++ b/branch_forward/tests/specs/no_merges.yml
@@ -0,0 +1,41 @@
+initialization:
+  steps:
+    - type: commit
+      empty: true
+      message: Introduce Harry
+      id: start
+    - type: commit
+      empty: true
+      message: Add about family
+
+    - type: branch
+      branch-name: with-ginny
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Add about Ginny
+
+    - type: checkout
+      branch-name: main
+    - type: commit
+      empty: true
+      message: Add cast.txt
+
+    - type: branch
+      branch-name: with-sally
+    - type: checkout
+      branch-name: with-sally
+    - type: commit
+      empty: true
+      message: Mention Sally
+
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Mention Ginny is single
+
+    - type: checkout
+      branch-name: main
+
diff --git a/branch_forward/tests/specs/other_branch_ff.yml b/branch_forward/tests/specs/other_branch_ff.yml
new file mode 100644
index 0000000..e7f6377
--- /dev/null
+++ b/branch_forward/tests/specs/other_branch_ff.yml
@@ -0,0 +1,53 @@
+initialization:
+  steps:
+    - type: commit
+      empty: true
+      message: Introduce Harry
+      id: start
+    - type: commit
+      empty: true
+      message: Add about family
+
+    - type: branch
+      branch-name: with-ginny
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Add about Ginny
+
+    - type: checkout
+      branch-name: main
+    - type: commit
+      empty: true
+      message: Add cast.txt
+
+    - type: branch
+      branch-name: with-sally
+    - type: checkout
+      branch-name: with-sally
+    - type: commit
+      empty: true
+      message: Mention Sally
+
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Mention Ginny is single
+
+    - type: checkout
+      branch-name: main
+    - type: branch
+      branch-name: with-ron
+    - type: checkout
+      branch-name: with-ron
+    - type: commit
+      empty: true
+      message: Mention Ron
+
+    - type: checkout
+      branch-name: main
+    - type: merge
+      branch-name: with-ron
+
diff --git a/branch_forward/tests/specs/other_branch_non_ff.yml b/branch_forward/tests/specs/other_branch_non_ff.yml
new file mode 100644
index 0000000..0bb536f
--- /dev/null
+++ b/branch_forward/tests/specs/other_branch_non_ff.yml
@@ -0,0 +1,43 @@
+initialization:
+  steps:
+    - type: commit
+      empty: true
+      message: Introduce Harry
+      id: start
+    - type: commit
+      empty: true
+      message: Add about family
+
+    - type: branch
+      branch-name: with-ginny
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Add about Ginny
+
+    - type: checkout
+      branch-name: main
+    - type: commit
+      empty: true
+      message: Add cast.txt
+
+    - type: branch
+      branch-name: with-sally
+    - type: checkout
+      branch-name: with-sally
+    - type: commit
+      empty: true
+      message: Mention Sally
+
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Mention Ginny is single
+
+    - type: checkout
+      branch-name: main
+    - type: merge
+      branch-name: with-ginny
+
diff --git a/branch_forward/tests/test_verify.py b/branch_forward/tests/test_verify.py
new file mode 100644
index 0000000..f124449
--- /dev/null
+++ b/branch_forward/tests/test_verify.py
@@ -0,0 +1,52 @@
+from git_autograder import GitAutograderStatus, GitAutograderTestLoader, assert_output
+
+from ..verify import (
+    FAST_FORWARD_REQUIRED,
+    ONLY_WITH_SALLY_MERGED,
+    verify,
+)
+
+REPOSITORY_NAME = "branch-forward"
+
+loader = GitAutograderTestLoader(__file__, REPOSITORY_NAME, verify)
+
+
+def test_success():
+    with loader.load("specs/base.yml", "start") as output:
+        assert_output(output, GitAutograderStatus.SUCCESSFUL)
+
+
+def test_no_merges():
+    with loader.load("specs/no_merges.yml", "start") as output:
+        assert_output(
+            output,
+            GitAutograderStatus.UNSUCCESSFUL,
+            [FAST_FORWARD_REQUIRED],
+        )
+
+
+def test_other_branch_non_ff():
+    with loader.load("specs/other_branch_non_ff.yml", "start") as output:
+        assert_output(
+            output,
+            GitAutograderStatus.UNSUCCESSFUL,
+            [FAST_FORWARD_REQUIRED],
+        )
+
+
+def test_other_branch_ff():
+    with loader.load("specs/other_branch_ff.yml", "start") as output:
+        assert_output(
+            output,
+            GitAutograderStatus.UNSUCCESSFUL,
+            [ONLY_WITH_SALLY_MERGED],
+        )
+
+
+def test_merge_with_sally_no_ff():
+    with loader.load("specs/merge_with_sally_no_ff.yml", "start") as output:
+        assert_output(
+            output,
+            GitAutograderStatus.UNSUCCESSFUL,
+            [FAST_FORWARD_REQUIRED],
+        )
diff --git a/branch_forward/verify.py b/branch_forward/verify.py
new file mode 100644
index 0000000..e10277d
--- /dev/null
+++ b/branch_forward/verify.py
@@ -0,0 +1,42 @@
+from git_autograder import (
+    GitAutograderExercise,
+    GitAutograderOutput,
+    GitAutograderStatus,
+)
+
+FAST_FORWARD_REQUIRED = (
+    "You must use a fast-forward merge to bring a branch into 'main'."
+)
+
+ONLY_WITH_SALLY_MERGED = (
+    "Only the 'with-sally' branch should be merged into 'main'. Do not merge other branches."
+)
+
+def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
+    main_branch = exercise.repo.branches.branch("main")
+    merge_logs = [
+        entry for entry in main_branch.reflog if entry.action.startswith("merge ")
+    ]
+
+    if not merge_logs:
+        raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
+
+    main_commits = list(main_branch.commits)
+    if any(len(commit.parents) > 1 for commit in main_commits):
+        raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
+
+    if any(entry.message != "Fast-forward" for entry in merge_logs):
+        raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
+
+    merged_branches = [entry.action[len("merge ") :] for entry in merge_logs]
+
+    if "with-sally" not in merged_branches:
+        raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
+
+    if any(branch != "with-sally" for branch in merged_branches):
+        raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
+
+    return exercise.to_output(
+        ["Great job fast-forward merging only 'with-sally' and cleaning up the branch!"],
+        GitAutograderStatus.SUCCESSFUL,
+    )

From 88cdc862cb85253fd8819a520674f4ed611a5b43 Mon Sep 17 00:00:00 2001
From: keerthigkaarthik <120106412+keerthigkaarthik@users.noreply.github.com>
Date: Fri, 14 Nov 2025 10:11:40 +0100
Subject: [PATCH 2/6] Change wrong answer message

---
 branch_forward/verify.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/branch_forward/verify.py b/branch_forward/verify.py
index e10277d..f05a389 100644
--- a/branch_forward/verify.py
+++ b/branch_forward/verify.py
@@ -9,7 +9,7 @@
 )
 
 ONLY_WITH_SALLY_MERGED = (
-    "Only the 'with-sally' branch should be merged into 'main'. Do not merge other branches."
+    "Only one of the two starting branches can be fast-forward merged into 'main'. Do not create new branches."
 )
 
 def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:

From d664fd36b09e4dc386c4b4c4b679ecbea283ec51 Mon Sep 17 00:00:00 2001
From: keerthigkaarthik <120106412+keerthigkaarthik@users.noreply.github.com>
Date: Fri, 14 Nov 2025 10:16:26 +0100
Subject: [PATCH 3/6] Add last empty line

---
 branch_forward/.gitmastery-exercise.json              | 2 +-
 branch_forward/README.md                              | 2 +-
 branch_forward/tests/specs/base.yml                   | 1 +
 branch_forward/tests/specs/merge_with_sally_no_ff.yml | 1 +
 branch_forward/tests/test_verify.py                   | 1 +
 branch_forward/verify.py                              | 1 +
 6 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/branch_forward/.gitmastery-exercise.json b/branch_forward/.gitmastery-exercise.json
index 63acafd..a68c6c0 100644
--- a/branch_forward/.gitmastery-exercise.json
+++ b/branch_forward/.gitmastery-exercise.json
@@ -14,4 +14,4 @@
     "create_fork": null,
     "init": true
   }
-}
\ No newline at end of file
+}
diff --git a/branch_forward/README.md b/branch_forward/README.md
index af774d7..f32c1fe 100644
--- a/branch_forward/README.md
+++ b/branch_forward/README.md
@@ -23,4 +23,4 @@ You are outlining a story and experimenting with different plotlines. Each versi
 
 Ensure you have switched to the destination branch before initiating the merge.
 
-</details>
\ No newline at end of file
+</details>
diff --git a/branch_forward/tests/specs/base.yml b/branch_forward/tests/specs/base.yml
index 99af44c..6ddea2c 100644
--- a/branch_forward/tests/specs/base.yml
+++ b/branch_forward/tests/specs/base.yml
@@ -40,3 +40,4 @@ initialization:
       branch-name: main
     - type: merge
       branch-name: with-sally
+
diff --git a/branch_forward/tests/specs/merge_with_sally_no_ff.yml b/branch_forward/tests/specs/merge_with_sally_no_ff.yml
index 1b76e03..75169f8 100644
--- a/branch_forward/tests/specs/merge_with_sally_no_ff.yml
+++ b/branch_forward/tests/specs/merge_with_sally_no_ff.yml
@@ -41,3 +41,4 @@ initialization:
     - type: merge
       branch-name: with-sally
       no-ff: true
+
diff --git a/branch_forward/tests/test_verify.py b/branch_forward/tests/test_verify.py
index f124449..95b68eb 100644
--- a/branch_forward/tests/test_verify.py
+++ b/branch_forward/tests/test_verify.py
@@ -50,3 +50,4 @@ def test_merge_with_sally_no_ff():
             GitAutograderStatus.UNSUCCESSFUL,
             [FAST_FORWARD_REQUIRED],
         )
+
diff --git a/branch_forward/verify.py b/branch_forward/verify.py
index f05a389..cc213b8 100644
--- a/branch_forward/verify.py
+++ b/branch_forward/verify.py
@@ -40,3 +40,4 @@ def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
         ["Great job fast-forward merging only 'with-sally' and cleaning up the branch!"],
         GitAutograderStatus.SUCCESSFUL,
     )
+

From da787860f9d7db665f435f936ca7ff8227da8a35 Mon Sep 17 00:00:00 2001
From: keerthigkaarthik <120106412+keerthigkaarthik@users.noreply.github.com>
Date: Tue, 25 Nov 2025 23:37:42 +0100
Subject: [PATCH 4/6] Apply changes from code review

---
 branch_forward/download.py                    |  6 +--
 .../tests/specs/with_sally_non_ff_then_ff.yml | 46 +++++++++++++++++++
 branch_forward/tests/test_verify.py           | 11 ++++-
 branch_forward/verify.py                      | 20 ++++----
 4 files changed, 68 insertions(+), 15 deletions(-)
 create mode 100644 branch_forward/tests/specs/with_sally_non_ff_then_ff.yml

diff --git a/branch_forward/download.py b/branch_forward/download.py
index 1eff523..e75ed57 100644
--- a/branch_forward/download.py
+++ b/branch_forward/download.py
@@ -1,9 +1,9 @@
-from exercise_utils.file import append_to_file
+from exercise_utils.file import append_to_file, create_or_update_file
 from exercise_utils.git import add, checkout, commit
 
 
 def setup(verbose: bool = False):
-    append_to_file(
+    create_or_update_file(
         "story.txt",
         """
         Harry was single.
@@ -32,7 +32,7 @@ def setup(verbose: bool = False):
     commit("Add about Ginny", verbose)
 
     checkout("main", False, verbose)
-    append_to_file(
+    create_or_update_file(
         "cast.txt",
         """
         Harry
diff --git a/branch_forward/tests/specs/with_sally_non_ff_then_ff.yml b/branch_forward/tests/specs/with_sally_non_ff_then_ff.yml
new file mode 100644
index 0000000..1464a99
--- /dev/null
+++ b/branch_forward/tests/specs/with_sally_non_ff_then_ff.yml
@@ -0,0 +1,46 @@
+initialization:
+  steps:
+    - type: commit
+      empty: true
+      message: Introduce Harry
+      id: start
+    - type: commit
+      empty: true
+      message: Add about family
+
+    - type: branch
+      branch-name: with-ginny
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Add about Ginny
+
+    - type: checkout
+      branch-name: main
+    - type: commit
+      empty: true
+      message: Add cast.txt
+
+    - type: branch
+      branch-name: with-sally
+    - type: checkout
+      branch-name: with-sally
+    - type: commit
+      empty: true
+      message: Mention Sally
+
+    - type: checkout
+      branch-name: with-ginny
+    - type: commit
+      empty: true
+      message: Mention Ginny is single
+
+    - type: checkout
+      branch-name: main
+    - type: bash
+      runs: |
+        git merge with-sally --no-ff -m "Non fast-forward merge"
+        git reset --hard 'HEAD^'
+        git merge with-sally
+
diff --git a/branch_forward/tests/test_verify.py b/branch_forward/tests/test_verify.py
index 95b68eb..8bac588 100644
--- a/branch_forward/tests/test_verify.py
+++ b/branch_forward/tests/test_verify.py
@@ -21,7 +21,7 @@ def test_no_merges():
         assert_output(
             output,
             GitAutograderStatus.UNSUCCESSFUL,
-            [FAST_FORWARD_REQUIRED],
+            [ONLY_WITH_SALLY_MERGED],
         )
 
 
@@ -30,7 +30,7 @@ def test_other_branch_non_ff():
         assert_output(
             output,
             GitAutograderStatus.UNSUCCESSFUL,
-            [FAST_FORWARD_REQUIRED],
+            [ONLY_WITH_SALLY_MERGED],
         )
 
 
@@ -51,3 +51,10 @@ def test_merge_with_sally_no_ff():
             [FAST_FORWARD_REQUIRED],
         )
 
+
+def test_merge_with_sally_fix_after_non_ff():
+    with loader.load(
+        "specs/with_sally_non_ff_then_ff.yml", "start"
+    ) as output:
+        assert_output(output, GitAutograderStatus.SUCCESSFUL)
+
diff --git a/branch_forward/verify.py b/branch_forward/verify.py
index cc213b8..bd74085 100644
--- a/branch_forward/verify.py
+++ b/branch_forward/verify.py
@@ -18,21 +18,21 @@ def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
         entry for entry in main_branch.reflog if entry.action.startswith("merge ")
     ]
 
-    if not merge_logs:
-        raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
-
-    main_commits = list(main_branch.commits)
-    if any(len(commit.parents) > 1 for commit in main_commits):
-        raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
-
-    if any(entry.message != "Fast-forward" for entry in merge_logs):
-        raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
-
     merged_branches = [entry.action[len("merge ") :] for entry in merge_logs]
 
     if "with-sally" not in merged_branches:
         raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
 
+    latest_with_sally_merge = next(
+        (entry for entry in merge_logs if entry.action == "merge with-sally"), None
+    )
+
+    if latest_with_sally_merge is None:
+        raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
+
+    if latest_with_sally_merge.message != "Fast-forward":
+        raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
+
     if any(branch != "with-sally" for branch in merged_branches):
         raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
 

From f54d88aff4ed42ba6c16b63f08f6643bedc66e87 Mon Sep 17 00:00:00 2001
From: keerthigkaarthik <120106412+keerthigkaarthik@users.noreply.github.com>
Date: Tue, 9 Dec 2025 14:22:37 +0100
Subject: [PATCH 5/6] Apply changes following code review

---
 ...f_then_ff.yml => reset_ginny_ff_sally.yml} |  5 +-
 branch_forward/tests/test_verify.py           |  4 +-
 branch_forward/verify.py                      | 46 +++++++++++++------
 3 files changed, 35 insertions(+), 20 deletions(-)
 rename branch_forward/tests/specs/{with_sally_non_ff_then_ff.yml => reset_ginny_ff_sally.yml} (90%)

diff --git a/branch_forward/tests/specs/with_sally_non_ff_then_ff.yml b/branch_forward/tests/specs/reset_ginny_ff_sally.yml
similarity index 90%
rename from branch_forward/tests/specs/with_sally_non_ff_then_ff.yml
rename to branch_forward/tests/specs/reset_ginny_ff_sally.yml
index 1464a99..a345350 100644
--- a/branch_forward/tests/specs/with_sally_non_ff_then_ff.yml
+++ b/branch_forward/tests/specs/reset_ginny_ff_sally.yml
@@ -40,7 +40,6 @@ initialization:
       branch-name: main
     - type: bash
       runs: |
-        git merge with-sally --no-ff -m "Non fast-forward merge"
+        git merge with-ginny
         git reset --hard 'HEAD^'
-        git merge with-sally
-
+        git merge with-sally
\ No newline at end of file
diff --git a/branch_forward/tests/test_verify.py b/branch_forward/tests/test_verify.py
index 8bac588..df476b6 100644
--- a/branch_forward/tests/test_verify.py
+++ b/branch_forward/tests/test_verify.py
@@ -52,9 +52,9 @@ def test_merge_with_sally_no_ff():
         )
 
 
-def test_merge_with_sally_fix_after_non_ff():
+def test_reset_ginny_ff_sally():
     with loader.load(
-        "specs/with_sally_non_ff_then_ff.yml", "start"
+        "specs/reset_ginny_ff_sally.yml", "start"
     ) as output:
         assert_output(output, GitAutograderStatus.SUCCESSFUL)
 
diff --git a/branch_forward/verify.py b/branch_forward/verify.py
index bd74085..898f4a4 100644
--- a/branch_forward/verify.py
+++ b/branch_forward/verify.py
@@ -12,32 +12,48 @@
     "Only one of the two starting branches can be fast-forward merged into 'main'. Do not create new branches."
 )
 
-def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
-    main_branch = exercise.repo.branches.branch("main")
-    merge_logs = [
-        entry for entry in main_branch.reflog if entry.action.startswith("merge ")
-    ]
-
-    merged_branches = [entry.action[len("merge ") :] for entry in merge_logs]
+EXPECTED_MAIN_COMMIT_MESSAGES = {
+    "Introduce Harry",
+    "Add about family",
+    "Add cast.txt",
+    "Mention Sally",
+}
 
-    if "with-sally" not in merged_branches:
-        raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
+def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
+    repo = exercise.repo.repo
+    head_commit = repo.head.commit
+    main_commits = list(repo.iter_commits("main"))
 
-    latest_with_sally_merge = next(
-        (entry for entry in merge_logs if entry.action == "merge with-sally"), None
+    sally_commit = next(
+        (commit for commit in main_commits if commit.message.strip() == "Mention Sally"),
+        None,
     )
+    if sally_commit is None:
+        raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
 
-    if latest_with_sally_merge is None:
+    # Confirm that the fast-forward landed exactly on the expected commit and did not
+    # introduce a merge commit.
+    if len(head_commit.parents) != 1:
         raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
 
-    if latest_with_sally_merge.message != "Fast-forward":
+    if head_commit.message.strip() != "Mention Sally":
+        raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
+
+    if any(len(commit.parents) > 1 for commit in main_commits):
         raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
 
-    if any(branch != "with-sally" for branch in merged_branches):
+    if len(main_commits) != len(EXPECTED_MAIN_COMMIT_MESSAGES):
+        raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
+
+    commit_messages = {commit.message.strip() for commit in main_commits}
+    if not commit_messages.issubset(EXPECTED_MAIN_COMMIT_MESSAGES):
+        raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
+
+    if "Mention Ginny is single" in commit_messages:
         raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
 
     return exercise.to_output(
-        ["Great job fast-forward merging only 'with-sally' and cleaning up the branch!"],
+        ["Great job fast-forward merging only 'with-sally'!"],
         GitAutograderStatus.SUCCESSFUL,
     )
 

From 4b3ca64cc64f4257162fa3add1043fdfb41f368f Mon Sep 17 00:00:00 2001
From: jovnc <95868357+jovnc@users.noreply.github.com>
Date: Sat, 13 Dec 2025 11:00:54 +0800
Subject: [PATCH 6/6] [branch-forward] Refactor verify.py and remove
 unnecessary test

---
 branch_forward/README.md                      |  9 +---
 .../tests/specs/reset_ginny_ff_sally.yml      | 45 -------------------
 branch_forward/tests/test_verify.py           |  8 ----
 branch_forward/verify.py                      | 32 +++++++------
 4 files changed, 20 insertions(+), 74 deletions(-)
 delete mode 100644 branch_forward/tests/specs/reset_ginny_ff_sally.yml

diff --git a/branch_forward/README.md b/branch_forward/README.md
index f32c1fe..55567b6 100644
--- a/branch_forward/README.md
+++ b/branch_forward/README.md
@@ -1,12 +1,6 @@
 # branch-forward
 
-You are outlining a story and experimenting with different plotlines. Each version lives on its own branch, and you now need to fold the right storyline back into `main` without cluttering the history.
-
-## Learning objectives
-
-- Identify when a branch can be fast-forward merged
-- Use fast-forward merges to keep the commit graph linear
-- [Fast-forward merges](https://nus-cs2103-ay2526s1.github.io/website/book/gitAndGithub/merge/index.html)
+You are writing the outline for a story. You now have two parallel storylines in two branches.
 
 ## Task
 
@@ -16,7 +10,6 @@ You are outlining a story and experimenting with different plotlines. Each versi
 
 ## Hints
 
-
 <details>
 
 <summary>Hint 1</summary>
diff --git a/branch_forward/tests/specs/reset_ginny_ff_sally.yml b/branch_forward/tests/specs/reset_ginny_ff_sally.yml
deleted file mode 100644
index a345350..0000000
--- a/branch_forward/tests/specs/reset_ginny_ff_sally.yml
+++ /dev/null
@@ -1,45 +0,0 @@
-initialization:
-  steps:
-    - type: commit
-      empty: true
-      message: Introduce Harry
-      id: start
-    - type: commit
-      empty: true
-      message: Add about family
-
-    - type: branch
-      branch-name: with-ginny
-    - type: checkout
-      branch-name: with-ginny
-    - type: commit
-      empty: true
-      message: Add about Ginny
-
-    - type: checkout
-      branch-name: main
-    - type: commit
-      empty: true
-      message: Add cast.txt
-
-    - type: branch
-      branch-name: with-sally
-    - type: checkout
-      branch-name: with-sally
-    - type: commit
-      empty: true
-      message: Mention Sally
-
-    - type: checkout
-      branch-name: with-ginny
-    - type: commit
-      empty: true
-      message: Mention Ginny is single
-
-    - type: checkout
-      branch-name: main
-    - type: bash
-      runs: |
-        git merge with-ginny
-        git reset --hard 'HEAD^'
-        git merge with-sally
\ No newline at end of file
diff --git a/branch_forward/tests/test_verify.py b/branch_forward/tests/test_verify.py
index df476b6..433727d 100644
--- a/branch_forward/tests/test_verify.py
+++ b/branch_forward/tests/test_verify.py
@@ -50,11 +50,3 @@ def test_merge_with_sally_no_ff():
             GitAutograderStatus.UNSUCCESSFUL,
             [FAST_FORWARD_REQUIRED],
         )
-
-
-def test_reset_ginny_ff_sally():
-    with loader.load(
-        "specs/reset_ginny_ff_sally.yml", "start"
-    ) as output:
-        assert_output(output, GitAutograderStatus.SUCCESSFUL)
-
diff --git a/branch_forward/verify.py b/branch_forward/verify.py
index 898f4a4..4874f07 100644
--- a/branch_forward/verify.py
+++ b/branch_forward/verify.py
@@ -1,4 +1,6 @@
+from typing import List, Optional
 from git_autograder import (
+    GitAutograderCommit,
     GitAutograderExercise,
     GitAutograderOutput,
     GitAutograderStatus,
@@ -8,9 +10,7 @@
     "You must use a fast-forward merge to bring a branch into 'main'."
 )
 
-ONLY_WITH_SALLY_MERGED = (
-    "Only one of the two starting branches can be fast-forward merged into 'main'. Do not create new branches."
-)
+ONLY_WITH_SALLY_MERGED = "Only one of the two starting branches can be fast-forward merged into 'main'. Do not create new branches."
 
 EXPECTED_MAIN_COMMIT_MESSAGES = {
     "Introduce Harry",
@@ -19,15 +19,22 @@
     "Mention Sally",
 }
 
+
+def get_commit_from_message(
+    commits: List[GitAutograderCommit], message: str
+) -> Optional[GitAutograderCommit]:
+    """Find a commit with the given message from a list of commits."""
+    for commit in commits:
+        if message.strip() == commit.commit.message.strip():
+            return commit
+    return None
+
+
 def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
-    repo = exercise.repo.repo
-    head_commit = repo.head.commit
-    main_commits = list(repo.iter_commits("main"))
+    main_commits = exercise.repo.branches.branch("main").commits
+    head_commit = exercise.repo.branches.branch("main").latest_commit
 
-    sally_commit = next(
-        (commit for commit in main_commits if commit.message.strip() == "Mention Sally"),
-        None,
-    )
+    sally_commit = get_commit_from_message(main_commits, "Mention Sally")
     if sally_commit is None:
         raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
 
@@ -36,7 +43,7 @@ def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
     if len(head_commit.parents) != 1:
         raise exercise.wrong_answer([FAST_FORWARD_REQUIRED])
 
-    if head_commit.message.strip() != "Mention Sally":
+    if head_commit.commit.message.strip() != "Mention Sally":
         raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
 
     if any(len(commit.parents) > 1 for commit in main_commits):
@@ -45,7 +52,7 @@ def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
     if len(main_commits) != len(EXPECTED_MAIN_COMMIT_MESSAGES):
         raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
 
-    commit_messages = {commit.message.strip() for commit in main_commits}
+    commit_messages = {commit.commit.message.strip() for commit in main_commits}
     if not commit_messages.issubset(EXPECTED_MAIN_COMMIT_MESSAGES):
         raise exercise.wrong_answer([ONLY_WITH_SALLY_MERGED])
 
@@ -56,4 +63,3 @@ def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
         ["Great job fast-forward merging only 'with-sally'!"],
         GitAutograderStatus.SUCCESSFUL,
     )
-