Add test for commit message format

Added test that checks if commits follow the 50/72 git
commit rule and if they are signed (git commit -s).
Fixes: #9, #14.

Signed-off-by: Laura Loghin <lauralg@amazon.com>

.buildkite/pipeline.yml

@@ -190,3 +190,16 @@ steps:
           privileged: true
           image: "rustvmm/dev:v6"
           always-pull: true
+
+  - label: "commit-format"
+    commands:
+      - pytest rust-vmm-ci/integration_tests/test_commit_format.py
+    retry:
+      automatic: false
+    agents:
+      os: linux
+    plugins:
+      - docker#v3.0.1:
+          image: "rustvmm/dev:v6"
+          always-pull: true
+          propagate-environment: true

integration_tests/test_commit_format.py

@@ -0,0 +1,62 @@
+# Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""Test the commit message format."""
+
+import os
+
+from utils import get_cmd_output
+
+COMMIT_TITLE_MAX_LEN = 50
+COMMIT_BODY_LINE_MAX_LEN = 72
+BASE_BRANCH = os.environ['BUILDKITE_PULL_REQUEST_BASE_BRANCH']
+
+
+def test_commit_format():
+    """
+    Checks commit message format for the current PR's commits.
+
+    Checks if commit messages follow the 50/72 git commit rule
+    [https://www.midori-global.com/blog/2018/04/02/git-50-72-rule]
+    and if commits are signed.
+    """
+    # Get hashes of PR's commits in their abbreviated form for
+    # a prettier printing.
+    shas_cmd = "git log --no-merges --pretty=%h --no-decorate " \
+               "{}..HEAD".format(BASE_BRANCH)
+    shas = get_cmd_output(shas_cmd)
+
+    for sha in shas.split():
+        message_cmd = "git show --pretty=format:%B -s " + sha
+        message = get_cmd_output(message_cmd)
+        message_lines = message.split("\n")
+        assert len(message_lines) >= 3,\
+            "The commit should contain at least 3 lines: title, blank " \
+            "line and a sign-off one. Please check: " \
+            "https://www.midori-global.com/blog/2018/04/02/git-50-72-rule."
+        title = message_lines[0]
+        assert message_lines[1] == "", "Commit title is divided into " \
+                                       "multiple lines. Please keep it " \
+                                       "one line long and make sure you " \
+                                       "add a blank line between title " \
+                                       "and description."
+        assert len(title) <= COMMIT_TITLE_MAX_LEN,\
+            "For commit '{}', title exceeds {} chars. " \
+            "Please keep it shorter.".format(sha, COMMIT_TITLE_MAX_LEN)
+
+        found_signed_off = False
+
+        for line in message_lines[2:]:
+            if line.startswith("Signed-off-by: "):
+                found_signed_off = True
+                # If we found `Signed-off-by` line, then it means
+                # the commit message ended and we don't want to check
+                # line lengths anymore for the current commit.
+                break
+            assert len(line) <= COMMIT_BODY_LINE_MAX_LEN,\
+                "For commit '{}', message line '{}' exceeds {} chars. " \
+                "Please keep it shorter or split it in " \
+                "multiple lines.".format(sha, line,
+                                         COMMIT_BODY_LINE_MAX_LEN)
+        assert found_signed_off, "Commit '{}' is not signed. " \
+                                 "Please run 'git commit -s --amend' " \
+                                 "on it.".format(sha)

integration_tests/test_coverage.py

@@ -13,6 +13,7 @@ if platform.machine() == "x86_64":
 elif platform.machine() == "aarch64":
     COVERAGE_CONFIG_PATH = os.path.join(REPO_ROOT_PATH, "coverage_config_aarch64.json")
 
+
 def _read_test_config():
     """
     Reads the config of the coverage for the repository being tested.

integration_tests/utils.py

@@ -1,6 +1,8 @@
 # Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 # SPDX-License-Identifier: Apache-2.0
+
 import os
+import subprocess
 
 
 def get_repo_root_path():
@@ -9,3 +11,11 @@ def get_repo_root_path():
     rust_vmm_ci_path = os.path.dirname(integration_tests_path)
 
     return os.path.dirname(rust_vmm_ci_path)
+
+
+def get_cmd_output(cmd):
+    """Returns stdout content of `cmd` command."""
+    cmd_out = subprocess.run(cmd, shell=True, check=True,
+                             stdout=subprocess.PIPE)
+    stdout = cmd_out.stdout.decode('utf-8')
+    return stdout