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(for a short intro of the basic concepts of Mercurial, see [:UnderstandingMercurial])

A repository is a directory (the repository directory or "repo" directory) which contains a subdirectory named .hg (dot hg) where Mercurial stores its internal data structures. Everything else (files and other subdirectories) in the repo directory is conceptually part of the [:WorkingDirectory:working directory], which is tracked by Mercurial (some files and subdirectories may be ignored. See [:.hgignore]).


1. Creation

An existing, already populated but yet untracked directory can be transformed into a repository with hg init, which creates and initializes the .hg subdirectory.

2. Tracking Files

A file in the working directory that shall be tracked by Mercurial must be added with hg add. [:LocalModifications:Local modifications] to tracked files in the working directory can be [:Commit:committed] with hg commit, which adds a new [:ChangeSet:changeset] to the repository by recording it in the .hg directory.

The working directory can be restored with hg update to any previously committed state by specifying the requested changeset with its [:ChangeSetID:changeset ID].

The last transaction in a repository can be undone with hg rollback (see ["Rollback"]).

3. Transferring Changesets and Cloning

Changesets can be transferred from one repository to another with hg pull, hg push, hg export and hg import (see [:Pull], [:Push], [:Export], [:Import], [:CommunicatingChanges]).

Repositories can be [:Clone:cloned] with hg clone.

4. Checking Integrity

Checking the internal integrity of a repository (the contents of .hg) can be done with hg verify.

5. Structure

The .hg directory of a repository contains (incomplete listing):

  • The [:Manifest:manifest] — Files .hg/store/00manifest.i and .hg/store/00manifest.d

    • Describes the file contents of the repository at a particular changeset ID. Stored in [:Revlog:revlog] format.

  • The [:Changelog:changelog] — Files .hg/store/00changelog.i and .hg/store/00changelog.d

    • Contains all changesets. Stored in revlog format.
  • A revlog per tracked file — Files .hg/store/data/<encoded path>.i and .hg/store/data/<encoded path>.d

    • <encoded path> is the path of the tracked file in the working directory, encoded according to [:CaseFoldingPlan].

  • The [:DirState:dirstate] — File .hg/dirstate

    • Tracks various information about the working directory.

Note that for small revlogs, the revlog data file (*.d) may be missing, because its content may be interleaved into the corresponding index file (*.i) (see also [:RevlogNG]).

6. Backup

Backing up a repository can be done by using push/pull/clone to a backup repository. A repository which is not actively written to (by other processes concurrently running on the computer) can be backed-up by backing-up the repo directory using normal directory/file backup procedures (like tar, zip, etc). The .hg directory is [:CaseFolding:case folding] tolerant, which means, it can for example be copied onto a FAT filesystem (see also [:BackUp], [:CaseFoldingPlan]).

7. See also


Repository (last edited 2013-03-25 18:30:23 by 208)