Add commit-msg git hook and update readme.

README.md

@@ -1,8 +1,8 @@
 # rust-vmm-ci
-
 The `rust-vmm-ci` repository contains [integration tests](#integration-tests)
 and [Buildkite pipeline](#buildkite-pipeline) definitions that are used for
-running the CI for all rust-vmm crates.
+running the CI for all rust-vmm crates, as well as [git hooks](#git-hooks)
+to ensure quality and consistency with the rust-vmm commit message standards.
 
 CI tests are executed on the container image maintained at [rust-vmm/rust-vmm-container repo](https://github.com/rust-vmm/rust-vmm-container) with builds available on [Docker Hub](https://hub.docker.com/r/rustvmm/dev/tags).
 
@@ -15,6 +15,7 @@ To run the integration tests defined in the pipeline as part of the CI:
 
 1. Add rust-vmm-ci as a git submodule to your repository
 
+Adding rust-vmm-ci to new repos:
 ```bash
 # Add rust-vmm-ci as a submodule. This will point to the latest rust-vmm-ci
 # commit from the main branch. The following command will also add a
@@ -25,6 +26,12 @@ git submodule add https://github.com/rust-vmm/rust-vmm-ci.git
 git commit -s -m "Added rust-vmm-ci as submodule"
 ```
 
+Initializing rust-vmm-ci in cloned rust-vmm repos with existing
+uninitialized rust-vmm-ci submodule:
+```bash
+git submodule update --init
+```
+
 2. Create the coverage test configuration file named
 `coverage_config_ARCH.json` in the root of the repository, where `ARCH` is the
 architecture of the machine.
@@ -122,6 +129,33 @@ triggering the CI on
 and [push](https://developer.github.com/v3/activity/events/types/#pushevent)
 events.
 
+## Git Hooks
+To ensure consistency and quality across commit messages in your repository, rust-vmm-ci
+includes git hooks located at `rust-vmm-ci/git-hooks/`. Hooks are programs
+that trigger actions at certain points in git's execution.
+
+### Commit-Msg
+This hook is designed to automatically check your commit messages against with the 
+rust-vmm commit message standards.
+
+To utilize this hook for checking commit messages in your local repository, follow 
+these steps:
+
+1. Copy the Hook
+After adding rust-vmm-ci as a submodule, copy the commit-msg hook from the submodule's
+git-hooks directory to your repository's .git/hooks directory. You can do this with
+the following command from the root of your repository:
+
+```shell
+cp rust-vmm-ci/git-hooks/commit-msg .git/hooks/
+```
+
+2. Make the Hook Executable
+For the hook to run, it must be executable. Change its permissions accordingly:
+```shell
+chmod +x .git/hooks/commit-msg
+```
+
 ## Buildkite Pipeline
 
 The [Buildkite](https://buildkite.com) pipeline is the definition of tests to

githooks/commit-msg

@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+"""
+Commit-msg hook to check the commit message format.
+Ensures commit messages do not have exceedingly long titles (maximum 60 characters for the title)
+and that commits are signed.
+"""
+
+import sys
+
+COMMIT_TITLE_MAX_LEN = 60
+COMMIT_BODY_LINE_MAX_LEN = 75
+
+def get_commit_message(commit_msg_filepath):
+    """Retrieve the commit message from the provided file path."""
+    with open(commit_msg_filepath, 'r') as file:
+        return file.read()
+
+def main(commit_msg_filepath):
+    message = get_commit_message(commit_msg_filepath)
+    message_lines = message.split("\n")
+
+    # Check for long commit title
+    if not message_lines or len(message_lines[0]) > COMMIT_TITLE_MAX_LEN:
+        print(f"Error: Commit title is too long (maximum {COMMIT_TITLE_MAX_LEN} characters allowed). Title: '{message_lines[0]}'")
+        sys.exit(1)
+
+    # Ensure there is a blank line following the title
+    if len(message_lines) < 3 or message_lines[1] != "":
+        error_line = "None" if len(message_lines) < 2 else message_lines[1]
+        print(f"Error: The commit message should contain at least 3 lines: title, blank line, and description/sign-off. Problematic line: '{error_line}'")
+        sys.exit(1)
+
+    # Check for a signed-off message
+    found_signed_off = False
+    for line in message_lines[2:]:
+        if line.startswith("Signed-off-by: "):
+            found_signed_off = True
+            break
+        if len(line) > COMMIT_BODY_LINE_MAX_LEN:
+            print(f"Error: Line in commit body exceeds {COMMIT_BODY_LINE_MAX_LEN} characters. Line: '{line}'")
+            sys.exit(1)
+
+    if not found_signed_off:
+        print("Error: Commit is not signed. Please sign off your commit by running 'git commit -s'.")
+        sys.exit(1)
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("Error: No commit message file path provided.")
+        sys.exit(1)
+    main(sys.argv[1])
+