[branch-bender] Add check for no fast forwarding

Author: woojiahao

branch_bender/README.md

@@ -8,7 +8,7 @@ You have been working on all of these changes on separate branches and you now w
 
 ### Task 1
 
-Merge the `feature/login` branch into `main` first.
+Merge the `feature/login` branch into `main` first. Make sure you do not use fast forwarding when merging!
 
 ### Task 2
 

branch_bender/tests/specs/base.yml

@@ -31,7 +31,10 @@ initialization:
 
     - type: merge
       branch-name: feature/login
+      no-ff: true
     - type: merge
       branch-name: feature/dashboard
+      no-ff: true
     - type: merge
       branch-name: feature/payments
+      no-ff: true

branch_bender/tests/specs/ff_fails.yml

@@ -0,0 +1,37 @@
+initialization:
+  steps:
+    - type: commit
+      empty: true
+      message: Empty commit
+      id: start
+
+    - type: branch
+      branch-name: feature/login
+    - type: commit
+      empty: true
+      message: Empty commit on feature/login
+    - type: checkout
+      branch-name: main
+
+    - type: branch
+      branch-name: feature/dashboard
+    - type: commit
+      empty: true
+      message: Empty commit on feature/dashboard
+    - type: checkout
+      branch-name: main
+
+    - type: branch
+      branch-name: feature/payments
+    - type: commit
+      empty: true
+      message: Empty commit on feature/payments
+    - type: checkout
+      branch-name: main
+
+    - type: merge
+      branch-name: feature/login
+    - type: merge
+      branch-name: feature/dashboard
+    - type: merge
+      branch-name: feature/payments

branch_bender/tests/specs/missing_merges.yml

@@ -31,5 +31,7 @@ initialization:
 
     - type: merge
       branch-name: feature/login
+      no-ff: true
     - type: merge
       branch-name: feature/dashboard
+      no-ff: true

branch_bender/tests/specs/not_dashboard_second.yml

@@ -31,7 +31,10 @@ initialization:
 
     - type: merge
       branch-name: feature/login
+      no-ff: true
     - type: merge
       branch-name: feature/payments
+      no-ff: true
     - type: merge
       branch-name: feature/dashboard
+      no-ff: true

branch_bender/tests/specs/not_login_first.yml

@@ -31,7 +31,10 @@ initialization:
 
     - type: merge
       branch-name: feature/dashboard
+      no-ff: true
     - type: merge
       branch-name: feature/login
+      no-ff: true
     - type: merge
       branch-name: feature/payments
+      no-ff: true

branch_bender/tests/specs/not_payments_last.yml

@@ -39,7 +39,10 @@ initialization:
 
     - type: merge
       branch-name: feature/login
+      no-ff: true
     - type: merge
       branch-name: feature/dashboard
+      no-ff: true
     - type: merge
       branch-name: other
+      no-ff: true

branch_bender/tests/test_verify.py

@@ -5,6 +5,7 @@
     FEATURE_LOGIN_MERGE_MISSING,
     FEATURE_PAYMENTS_MERGE_MISSING,
     MISSING_MERGES,
+    NO_FAST_FORWARDING,
     NO_MERGES,
     NOT_ON_MAIN,
     RESET_MESSAGE,
@@ -22,6 +23,15 @@ def test_base():
         assert_output(output, GitAutograderStatus.SUCCESSFUL)
 
 
+def test_ff_fails():
+    with loader.load("specs/ff_fails.yml", "start") as output:
+        assert_output(
+            output,
+            GitAutograderStatus.UNSUCCESSFUL,
+            [NO_FAST_FORWARDING.format(branch_name="feature/login"), RESET_MESSAGE],
+        )
+
+
 def test_no_merges():
     with loader.load("specs/no_merges.yml", "start") as output:
         assert_output(output, GitAutograderStatus.UNSUCCESSFUL, [NO_MERGES])

branch_bender/verify.py

@@ -11,6 +11,7 @@
 DETACHED_HEAD = "You should not be in a detached HEAD state! Use git checkout main to get back to main"
 MISSING_MERGES = "You are missing some merges"
 NO_MERGES = "You need to start merging the feature branches."
+NO_FAST_FORWARDING = "You cannot use fast forwarding on {branch_name} when merging."
 WRONG_MERGE_ORDER = "You should have merged {branch_name} first. The expected order is feature/login, then feature/dashboard, and last feature/payments"
 FEATURE_LOGIN_MERGE_MISSING = "You should have merged feature/login first."
 FEATURE_DASHBOARD_MERGE_MISSING = "You should have merged feature/dashboard next."
@@ -31,6 +32,7 @@ def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
 
     main_reflog = main_branch.reflog
     merge_logs = [entry for entry in main_reflog if entry.action.startswith("merge")]
+    messages = [entry.message for entry in merge_logs][::-1]
     merge_order = [entry.action[len("merge ") :] for entry in merge_logs][::-1]
 
     if len(merge_order) == 0:
@@ -42,12 +44,27 @@ def verify(exercise: GitAutograderExercise) -> GitAutograderOutput:
     if merge_order[0] != "feature/login":
         raise exercise.wrong_answer([FEATURE_LOGIN_MERGE_MISSING, RESET_MESSAGE])
 
+    if messages[0] == "Fast-forward":
+        raise exercise.wrong_answer(
+            [NO_FAST_FORWARDING.format(branch_name="feature/login"), RESET_MESSAGE]
+        )
+
     if merge_order[1] != "feature/dashboard":
         raise exercise.wrong_answer([FEATURE_DASHBOARD_MERGE_MISSING, RESET_MESSAGE])
 
+    if messages[1] == "Fast-forward":
+        raise exercise.wrong_answer(
+            [NO_FAST_FORWARDING.format(branch_name="feature/dashboard"), RESET_MESSAGE]
+        )
+
     if merge_order[2] != "feature/payments":
         raise exercise.wrong_answer([FEATURE_PAYMENTS_MERGE_MISSING, RESET_MESSAGE])
 
+    if messages[2] == "Fast-forward":
+        raise exercise.wrong_answer(
+            [NO_FAST_FORWARDING.format(branch_name="feature/payments"), RESET_MESSAGE]
+        )
+
     return exercise.to_output(
         [
             "Great work with merging the branches in order! Try running the HTML files locally!"