rewrite-log

Tune a bit the extdiff toplevel comments/samples.

* Capitalize the first letter of all sentences

* Add an example for GNU diff(1) 'context diff' mode.

* Explain the requirement for separate cmd.xxx and opts.xxx
  options in .hgrc, which hopefully will guard against users
  trying to add:

      [extdiff]
      # Add a new Mercurial command called `cdiff', which calls
      # GNU diff(1) in 'context diff' mode.
      cmd.cdiff = diff -Nprc5

  which fails for recent crew builds with:

      $ hg cdiff .
      making snapshot of 1 files from rev 07dc4a569f4e
      making snapshot of 1 files from working dir
      diff -Nprc5: not found

  The correct way to do this is by separating the cmd.cdiff and
  opts.cdiff parts like this:

      [extdiff]
      # Add a new Mercurial command called `cdiff', which calls
      # GNU diff(1) in 'context diff' mode.
      cmd.cdiff = diff
      opts.cdiff = -Nprc5

  so add it as a new example and explicitly describe it in the
  extdiff comments.

#!/usr/bin/env python
import sys, os
from mercurial import hg

f = sys.argv[1]

r1 = hg.revlog(open, f + ".i", f + ".d")
r2 = hg.revlog(open, f + ".i2", f + ".d2")

tr = hg.transaction(open, "journal")

for i in xrange(r1.count()):
    n = r1.node(i)
    p1, p2 = r1.parents(n)
    l = r1.linkrev(n)
    t = r1.revision(n)
    n2 = r2.addrevision(t, tr, l, p1, p2)
tr.close()

os.rename(f + ".i", f + ".i.old")
os.rename(f + ".d", f + ".d.old")
os.rename(f + ".i2", f + ".i")
os.rename(f + ".d2", f + ".d")