[PATCH v2] backout: make help more explicit about what backout does

[Kevin Bullock]

On 2 Feb 2011, at 6:24 PM, Jonathan Nieder wrote:

> # HG changeset patch
> # User Jonathan Nieder <jrnieder at gmail.com>
> # Date 1296692409 21600
> # Node ID d2f1fa1b002f11e972c11434a8c9414ad53bd523
> # Parent  6bf8d48bec8e1ab2e0462ce14a914d06e64f7117
> backout: make help more explicit about what backout does
> 
> The help for backout explains:
> 
>    The backout command merges the reverse effect of the reverted
>    changeset into the working directory.
> 
> Unfortunately, that does not make it obvious to a newcomer what the
> backout command does.  Since it performs a 3-way merge, what is the
> common ancestor?  Will the result be automatically committed?  What is
> this reverted changeset --- is it the rev passed with -r on the
> command line or its inverse?
> 
> So try to clarify the description, avoiding jargon and being
> explicit about what happens from the user's perspective.
> 
> Thanks to Gilles Moris and timeless for help.
> 
> diff --git a/mercurial/commands.py b/mercurial/commands.py
> --- a/mercurial/commands.py
> +++ b/mercurial/commands.py
> @@ -204,26 +204,24 @@
> def backout(ui, repo, node=None, rev=None, **opts):
>     '''reverse effect of earlier changeset
> 
> -    The backout command merges the reverse effect of the reverted
> -    changeset into the working directory.
> -
> -    With the --merge option, it first commits the reverted changes
> -    as a new changeset. This new changeset is a child of the reverted
> -    changeset.
> -    The --merge option remembers the parent of the working directory
> -    before starting the backout, then merges the new head with that
> -    changeset afterwards.
> -    This will result in an explicit merge in the history.
> -
> -    If you backout a changeset other than the original parent of the
> -    working directory, the result of this merge is not committed,
> -    as with a normal merge. Otherwise, no merge is needed and the
> -    commit is automatic.
> -
> -    Note that the default behavior (without --merge) has changed in
> -    version 1.7. To restore the previous default behavior, use
> -    :hg:`backout --merge` and then :hg:`update --clean .` to get rid of
> -    the ongoing merge.
> +    Prepare a new changeset with the effect of REV undone in the
> +    current working directory.
> +
> +    If REV is the tip, then this changeset is committed automatically.

Is this accurate? Isn't the backout automatically committed if REV is a branch head, but -not- tip?

> +
> +    Otherwise, hg needs to merge the changes and you can inspect
> +    them before committing.
> +    By default, the pending changeset will have one parent,
> +    maintaining a linear history.

Just a nit: the line-breaking here is weird. Are you starting a new paragraph or not? Maybe something like this:

--
If REV is the tip [a branch head?], then this changeset is committed automatically.
Otherwise, the backout changes are merged with tip, and the result is
left in the working directory so that it can be inspected before
committing.

By default, the backout changeset will have just one parent, maintaining
a linear history. With the --merge option, first a new changeset is
committed as a child of REV that undoes its changes. This backout
changeset is then merged as normal with the working directory parent.
--

Okay, that was more than a nit, that was a rewording. :)

pacem in terris / mir / shanti / salaam / heiwa
pacem in terris / mir / shanti / salaam / heiwa
Kevin R. Bullock