How to use the command 'hg commit' (with examples)

The ‘hg commit’ command is central to managing code changes in the Mercurial version control system. It allows users to take a snapshot of modified files within a repository, thus recording the current state of these files. This snapshot is known as a commit, and it helps in preserving and documenting the changes made to the project files over time. This operation is essential for maintaining a historical record of a project’s development, facilitating collaborative work, and enabling easy reversion to previous project states if needed.

Use case 1: Commit staged files to the repository

Code:

hg commit

Motivation:
Committing staged files without specifying any additional options is the most straightforward use case. When you’ve made changes and staged all the files that need to capture these modifications, you use this command to save all amendments. This might be done after completing a set of tasks or fixes, making it a frequent operation large projects or individual developments.

Explanation:
The command ‘hg commit’ by itself identifies which files have been marked or staged for versioning, recording their current state in the repository. It is used to confirm and save these changes, allowing collaborators and yourself to access or revert to them as needed.

Example Output:

Committing changes
Added: path/to/added_file
Modified: path/to/modified_file
Removed: path/to/removed_file
Commit was successful.

Use case 2: Commit a specific file or directory

Code:

hg commit path/to/file_or_directory

Motivation:
Sometimes, changes to only specific files or directories need to be committed because they represent a logical portion of the ongoing work. This is particularly useful in a scenario where you might be working on different features or fixes simultaneously, and you wish to commit one section to avoid conflicts.

Explanation:
By specifying the path to a file or directory, you are instructing Mercurial to only create a commit with changes in those specified paths. This selective committing ensures only related changes are recorded together, which enhances tracking and division of work.

Example Output:

Committing changes
Modified: path/to/file_or_directory/modified_file
Commit was successful.

Use case 3: Commit with a specific message

Code:

hg commit --message "Fixed bug in calculation"

Motivation:
Including a commit message is crucial as it provides context and rationale for the changes, which is invaluable when reviewing commit history. This is particularly important in collaborative projects where others need to understand the intent and scope of your changes quickly.

Explanation:
The ‘–message’ option followed by a string allows you to add a description to your commit. The text should be concise yet descriptive enough that someone unfamiliar with the changes can understand what was done and why.

Example Output:

Committing changes
Added: path/to/new_file
Commit was successful with message: Fixed bug in calculation

Use case 4: Commit all files matching a specified pattern

Code:

hg commit --include "*.txt"

Motivation:
There might be situations where you only want to commit files of a certain type or pattern, such as logs or specific data files that you have modified but not all source code files. This can help in managing the commit process efficiently, especially in projects with numerous file types.

Explanation:
The ‘–include’ option allows you to specify a pattern. Only files that match this pattern will be included in the commit. Here, ‘*.txt’ would match all text files within the current directory and commit only those changes.

Example Output:

Committing changes
Modified: data/some_file.txt
Modified: notes/some_notes_file.txt
Commit was successful.

Use case 5: Commit all files, excluding those that match a specified pattern

Code:

hg commit --exclude "*.log"

Motivation:
Excluding files from a commit can be very useful when you have generated output files like logs or temporary files that don’t need to be versioned. This ensures only relevant and meaningful changes are archived in the version history.

Explanation:
The ‘–exclude’ option is used to specify a pattern of file types not to be included in the commit process. Here, ‘*.log’ indicates that any file ending with .log should be ignored while committing changes.

Example Output:

Committing changes
Modified: source/some_source_file.c
Modified: docs/documentation.md
Commit was successful.

Use case 6: Commit using the interactive mode

Code:

hg commit --interactive

Motivation:
Interactive committing is useful when you want to review and selectively commit portions of changes from your working directory. This gives you control over each part of your changes, which makes for a more detailed and accurate commit log.

Explanation:
The ‘–interactive’ option allows a manual review of changes before committing, prompting users to choose which files or changes should be included in the commit. This granular approach is particularly useful in large projects where changes are many and varied, often going hand-in-hand with code reviews.

Example Output:

Select changes to commit:

y - stage this hunk for commit
n - do not stage this hunk for commit
q - quit; do not commit
y, n, q> y
Commit was successful.

Conclusion:

The ‘hg commit’ command in Mercurial is an essential tool that aids in maintaining an organized and comprehensive history of your project. Whether you’re committing all changes, specifying particular files, using descriptive messages, or filtering commits based on patterns, understanding how to leverage these command variations can significantly enhance your workflow efficiency and project organization.