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Hg-Git Mercurial Plugin

This is the Hg-Git plugin for Mercurial, adding the ability to push and pull to/from a Git server repository from Hg. This means you can collaborate on Git based projects from Hg, or use a Git server as a collaboration point for a team with developers using both Git and Hg.

The Hg-Git plugin can convert commits/changesets losslessly from one system to another, so you can push via an Hg repository and another Hg client can pull it and their changeset node ids will be identical - Mercurial data does not get lost in translation. It is intended that Hg users may wish to use this to collaborate even if no Git users are involved in the project, and it may even provide some advantages if you're using Bookmarks (see below).

Dependencies

This plugin is implemented entirely in Python - there are no Git binary dependencies, you do not need to have Git installed on your system. The only dependencies are Mercurial and Dulwich. The plugin is known to work on Hg versions 1.9.3 through 2.3.1 and requires at least Dulwich 0.8.6.

Usage

You can clone a Git repository from Hg by running hg clone <url> [dest]. For example, if you were to run

$ hg clone git://github.com/schacon/hg-git.git

Hg-Git would clone the repository and convert it to an Hg repository for you.

If you want to clone a github repository for later pushing (or any other repository you access via ssh), you need to convert the ssh url to a format with an explicit protocol prefix. For example, the git url with push access

[email protected]:schacon/hg-git.git

would read

git+ssh://[email protected]/schacon/hg-git.git

(Mind the switch from colon to slash after the host!)

Your clone command would thus look like this:

$ hg clone git+ssh://[email protected]/schacon/hg-git.git

If you are starting from an existing Hg repository, you have to set up a Git repository somewhere that you have push access to, add a path entry for it in your .hg/hgrc file, and then run hg push [name] from within your repository. For example:

$ cd hg-git # (an Hg repository)
$ # edit .hg/hgrc and add the target git url in the paths section
$ hg push

This will convert all your Hg data into Git objects and push them to the Git server.

Now that you have an Hg repository that can push/pull to/from a Git repository, you can fetch updates with hg pull.

$ hg pull

That will pull down any commits that have been pushed to the server in the meantime and give you a new head that you can merge in.

Hg-Git can also be used to convert a Mercurial repository to Git. You can use a local repository or a remote repository accessed via SSH, HTTP or HTTPS. Use the following commands to convert the repository (it assumes your running this in $HOME).

$ mkdir git-repo; cd git-repo; git init; cd ..
$ cd hg-repo
$ hg bookmarks hg
$ hg push ../git-repo

The hg bookmark is necessary to prevent problems as otherwise hg-git pushes to the currently checked out branch confusing Git. This will create a branch named hg in the Git repository. To get the changes in master use the following command (only necessary in the first run, later just use git merge or rebase).

$ cd git-repo
$ git checkout -b master hg

To import new changesets into the Git repository just rerun the hg push command and then use git merge or git rebase in your Git repository.

Commands

gclear

TODO

gimport

TODO

gexport

TODO

git-cleanup

TODO

Hg Bookmarks Integration

Hg-Git pushes your bookmarks up to the Git server as branches and will pull Git branches down and set them up as bookmarks.

Installing

Clone this repository somewhere and make the 'extensions' section in your ~/.hgrc file look something like this:

[extensions]
hggit = [path-to]/hg-git/hggit

That will enable the Hg-Git extension for you.

This plugin is currently tested against the following Mercurial versions:

  • 1.9.3
  • 2.0.2
  • 2.1.2
  • 2.2.3
  • 2.3.1

Configuration

git.intree

hg-git keeps a git repository clone for reading and updating. By default, the git clone is the subdirectory git in your local Mercurial repository. If you would like this git clone to be at the same level of your Mercurial repository instead (named .git), add the following to your hgrc:

[git]
intree = True

git.authors

Git uses a strict convention for "author names" when representing changesets, using the form [realname] [email address]. Mercurial encourages this convention as well but is not as strict, so it's not uncommon for a Mercurial repo to have authors listed as simple usernames. hg-git by default will translate such names using the email address none@none, which then shows up unpleasantly on GitHub as "illegal email address".

The git.authors option provides for an "authors translation file" that will be used during outgoing transfers from mercurial to git only, by modifying hgrc as such:

[git]
authors = authors.txt

Where authors.txt is the name of a text file containing author name translations, one per each line, using the following format:

johnny = John Smith <[email protected]>
dougie = Doug Johnson <[email protected]>

Empty lines and lines starting with a "#" are ignored.

It should be noted that this translation is on the hg->git side only. Changesets coming from Git back to Mercurial will not translate back into hg usernames, so it's best that the same username/email combination be used on both the hg and git sides; the author file is mostly useful for translating legacy changesets.

git.branch_bookmark_suffix

hg-git does not convert between Mercurial named branches and git branches as the two are conceptually different; instead, it uses Mercurial bookmarks to represent the concept of a git branch. Therefore, when translating an hg repo over to git, you typically need to create bookmarks to mirror all the named branches that you'd like to see transferred over to git. The major caveat with this is that you can't use the same name for your bookmark as that of the named branch, and furthermore there's no feasible way to rename a branch in Mercurial. For the use case where one would like to transfer an hg repo over to git, and maintain the same named branches as are present on the hg side, the branch_bookmark_suffix might be all that's needed. This presents a string "suffix" that will be recognized on each bookmark name, and stripped off as the bookmark is translated to a git branch:

[git]
branch_bookmark_suffix=_bookmark

Above, if an hg repo had a named branch called release_6_maintenance, you could then link it to a bookmark called release_6_maintenance_bookmark. hg-git will then strip off the _bookmark suffix from this bookmark name, and create a git branch called release_6_maintenance. When pulling back from git to hg, the _bookmark suffix is then applied back, if and only if an hg named branch of that name exists. E.g., when changes to the release_6_maintenance branch are checked into git, these will be placed into the release_6_maintenance_bookmark bookmark on hg. But if a new branch called release_7_maintenance were pulled over to hg, and there was not a release_7_maintenance named branch already, the bookmark will be named release_7_maintenance with no usage of the suffix.

The branch_bookmark_suffix option is, like the authors option, intended for migrating legacy hg named branches. Going forward, an hg repo that is to be linked with a git repo should only use bookmarks for named branching.