Now `repo download . 1402` would download the change numbered 1402
into the current project and check it out for the user, using a
detached HEAD. `repo sync .` would back out of the change and
return to the upstream version.
Multiple projects can be fetched at once by listing them out on
the command line as different arguments.
Individual patch sets can be selected by adding a '/n' to indicate
the n-th patch set should be downloaded instead of the default of
patch set 1.
Signed-off-by: Shawn O. Pearce <sop@google.com>
