Sometimes you might have a patch from someone else that you want to submit to the buildbot. For example, a user may have created a patch to fix some specific bug and sent it to you by email. You've inspected the patch and suspect that it might do the job (and have at least confirmed that it doesn't do anything evil). Now you want to test it out.
One approach would be to check out a new local tree, apply the patch, run your local tests, then use “buildbot try” to run the tests on other platforms. An alternate approach is to use the buildbot try --diff form to have the buildbot test the patch without using a local tree.
This form takes a --diff argument which points to a file that contains the patch you want to apply. By default this patch will be applied to the TRUNK revision, but if you give the optional --baserev argument, a tree of the given revision will be used as a starting point instead of TRUNK.
You can also use buildbot try --diff=- to read the patch from stdin.
Each patch has a “patchlevel” associated with it. This indicates the number of slashes (and preceding pathnames) that should be stripped before applying the diff. This exactly corresponds to the -p or --strip argument to the patch utility. By default buildbot try --diff uses a patchlevel of 0, but you can override this with the -p argument.
When you use --diff, you do not need to use any of the other options that relate to a local tree, specifically --vc, --try-topfile, or --try-topdir. These options will be ignored. Of course you must still specify how to get to the buildmaster (with --connect, --tryhost, etc).