How to Use the Command 'hg push' (with Examples)

The hg push command is a fundamental feature of the Mercurial version control system, enabling users to transmit changes from a local repository to a remote repository. This operation is critical for collaboration in software development, where engineers share and integrate code changes. Understanding how to use hg push effectively can significantly enhance a developer’s productivity and ability to collaborate seamlessly with team members.

Use Case 1: Push Changes to the “Default” Remote Path

Code:

hg push

Motivation:
Pushing changes to the “default” remote path is the most common and straightforward method of sharing updates in a decentralized version control system like Mercurial. In most setups, the “default” path is configured to point to the central repository, where team members expect the latest changes. This ensures that everyone is working with the most recent updates, reducing the chances of conflicts and miscommunication.

Explanation:
The command hg push without any additional arguments assumes that there is a pre-configured remote path designated as “default” in the repository’s configuration file (.hg/hgrc). By executing this command, you instruct Mercurial to push the latest changes from your local repository to this pre-defined remote location. This is typically configured when you initially clone a repository, making it the easiest way to sync updates with minimal overhead.

Example Output:

pushing to https://example.com/repo
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
added 5 changesets with 10 changes to 5 files

Use Case 2: Push Changes to a Specified Remote Repository

Code:

hg push path/to/destination_repository

Motivation:
Specifying a particular remote repository path is necessary when working with multiple remotes or when a project involves various repositories for different purposes (e.g., development, testing, and production). Developers might also push to a colleague’s repository or a different branch location, which requires explicit path specification.

Explanation:
In this command, hg push, followed by the path to the desired destination repository, allows you to bypass the default setting and direct changes to a specified target. This path can be a URL or a file path indicating the remote repository’s location. This flexibility is essential when managing complex projects or collaborating with other developers in a non-linear workflow.

Example Output:

pushing to /path/to/destination_repository
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
added 3 changesets with 15 changes to 10 files

Use Case 3: Push a New Branch if It Does Not Exist

Code:

hg push --new-branch

Motivation:
This option caters to scenarios where developers need to create and share new branches of development in a project. By default, Mercurial does not push new branches unless explicitly instructed to do so. This prevents accidental proliferation of branches, which can lead to confusion and clutter in a shared repository.

Explanation:
The --new-branch argument explicitly requests Mercurial to push a branch that is currently non-existent in the remote repository. This is a safeguard to ensure that branches are only created intentionally, maintaining the repository’s integrity and organization. This is especially useful in active development environments where branching strategies dictate workflow.

Example Output:

pushing to https://example.com/repo
searching for changes
remote: adding branch new-feature
remote: adding changesets
remote: adding manifests
remote: adding file changes
added 1 changesets with 1 changes to 1 files

Use Case 4: Specify a Specific Revision Changeset to Push

Code:

hg push --rev revision

Motivation:
There are situations where a developer needs to push only a specific revision, such as a hotfix, without including later changes that are not yet ready or require further testing. This fine-grained control ensures that only the necessary updates are reflected in the remote repository.

Explanation:
By using the --rev (or -r) argument followed by the specific revision identifier (which can be changeset ID, a tag, or branch), the push command is constrained to that specified revision and all its ancestors. This targeted approach avoids pushing unintended subsequent changes that may be present in the local repository.

Example Output:

pushing to https://example.com/repo
searching for changes
pushing changeset 1234abcd
remote: adding changesets
remote: adding manifests
remote: adding file changes
added 1 changesets with 2 changes to 1 files

Use Case 5: Specify a Specific Branch to Push

Code:

hg push --branch branch

Motivation:
In projects with multiple active branches, it might be vital to push updates for a particular branch, without affecting others. This is crucial where different branches are used for particular phases of development or are allocated to specific teams or individuals.

Explanation:
With the --branch option, you specify the exact branch that needs to be pushed to the remote repository. This ensures focused synchronization of only the branch you are working on, safeguarding uncommitted work on other branches. This is highly valuable in continuous integration/continuous deployment (CI/CD) workflows.

Example Output:

pushing to https://example.com/repo
searching for changes
pushing branch feature-login
remote: adding changesets
remote: adding manifests
remote: adding file changes
added 4 changesets with 8 changes to 3 files

Use Case 6: Specify a Specific Bookmark to Push

Code:

hg push --bookmark bookmark

Motivation:
Utilizing bookmarks in Mercurial facilitates a way to track movements in a decentralized workflow similar to git branches but with a lighter weight. Pushing specific bookmarks ensures that references aligned with certain feature developments or bug fixes are shared, keeping the work delineated and organized.

Explanation:
In this context, --bookmark directs the push to include only changes associated with a specific bookmark. Bookmarks act as pseudo-branches and help maintain ephemeral references to particular revisions. This flexibility is ideal for teams that rely on bookmark-based workflow practices for agile development.

Example Output:

pushing to https://example.com/repo
searching for changes
pushing bookmark featureA
remote: adding changesets
remote: adding manifests
remote: adding file changes
added 2 changesets with 5 changes to 2 files

Conclusion:

Each invocation of the hg push command caters to distinct needs that arise in the course of development workflow, emphasizing the adaptability of Mercurial. Whether it involves pushing general updates to a main repository, sharing specific revisions or branches for isolated discussions, or managing bookmarks for lightweight project navigation, the hg push command serves as a versatile tool for enhancing collaboration and efficiency in software development processes.