"git p4" updates.

* ld/git-p4-updates:
  git-p4: auto-size the block
  git-p4: narrow the scope of exceptions caught when parsing an int
  git-p4: raise exceptions from p4CmdList based on error from p4 server
  git-p4: better error reporting when p4 fails
  git-p4: add option to disable syncing of p4/master with p4
  git-p4: disable-rebase: allow setting this via configuration
  git-p4: add options --commit and --disable-rebase