branchmap: handle nullrev in setcachedata
906be86990 recently changed to switch from:
self._rbcrevs[rbcrevidx:rbcrevidx + _rbcrecsize] = rec
to
pack_into(_rbcrecfmt, self._rbcrevs, rbcrevidx, node, branchidx)
This causes an exception if rbcrevidx is -1 (i.e. the nullrev). The old code
handled this because python handles out of bound sets to arrays gracefully. The
new code throws because the self._rbcrevs buffer isn't long enough to write 8
bytes to. Normally it would've been resized by the immediately preceding line,
but because the 0 length buffer is greater than the idx (-1) times the size, no
resize happens.
Setting the branch for the nullrev doesn't make sense anyway, so let's skip it.
This was caught by external tests in the Facebook extensions repo, but I've
added a test here that catches the issue.
#!/usr/bin/env python
#
# An example hgweb CGI script, edit as necessary
# See also https://mercurial-scm.org/wiki/PublishingRepositories
# Path to repo or hgweb config to serve (see 'hg help hgweb')
config = "/path/to/repo/or/config"
# Uncomment and adjust if Mercurial is not installed system-wide
# (consult "installed modules" path from 'hg debuginstall'):
#import sys; sys.path.insert(0, "/path/to/python/lib")
# Uncomment to send python tracebacks to the browser if an error occurs:
#import cgitb; cgitb.enable()
from mercurial import demandimport; demandimport.enable()
from mercurial.hgweb import hgweb, wsgicgi
application = hgweb(config)
wsgicgi.launch(application)