The working directory is the top-level directory in a repository, in which the plain versions of files are available to read, edit and build. Files in the working directory are usually from the tip, but may be from older revisions, or modified and not yet committed. The working directory is sometimes called the "working copy."
1. Manipulating the Working Directory
It’s useful to think of the working directory as "the changeset I’m about to commit". If the working directory has no local modifications it is said to be clean.
Use hg revert to discard all local modifications (see revert).
To remove all files from the working directory (not the repository!), you can do
hg update null
A branch name can be set for the working directory.
Mercurial tracks various information about the working directory (see DirState).
A working directory has one or two parent revisions. The parent revision (or revisions) will become the parent revisions of the new revision which will eventually be created by a commit of the local modifications.
An hg update will change the parent revision, whereas hg revert will only modify the content of the working directory.
A working directory will only have two parent revisions as the result of a merge, but only until that merge has been committed.
Immediately after a commit (or after an update -C), the working directory has exactly one parent revision, namely the newly committed (or updated-to) changeset. This is even the case if the newly committed changeset was a merge.
The command hg parents (without a revision specifier) lists the parent revision(s) of the working directory.
Example output for a single parent (no uncommitted merge):
$ hg parents changeset: 2:86794f718fb1 tag: tip user: email@example.com date: Mon May 05 01:20:46 2008 +0200 summary: Express great joy at existence of Mercurial
Example output for two parent revisions (after an uncommitted merge):
$ hg parents changeset: 2:c3844fde99f0 user: firstname.lastname@example.org date: Tue May 06 20:10:35 2008 +0200 summary: Add description of hello.c changeset: 3:86794f718fb1 tag: tip parent: 1:82e55d328c8c user: email@example.com date: Mon May 05 01:20:46 2008 +0200 summary: Express great joy at existence of Mercurial
3. When an update is needed
There are several ways to see if an update of your working directory is needed (see related mailing list thread):
To see the delta between the working directory and the tip, do:
hg diff -r tip
To see what patches would be applied to the working directory on an update do:
hg log -r tip:.
If the working directory is at the tip (that is, no update needed)
will write "tip" after the changeset id.