index: make capacity argument to nt_init be measured in revisions
The nodetree's internal capacity field is measures in nodetree nodes,
which is not something the caller should have to know about.
Differential Revision: https://phab.mercurial-scm.org/D4166
#require execbit
$ hg init repo
$ cd repo
$ echo foo > foo
$ chmod 644 foo
$ hg ci -qAm '644'
$ chmod 755 foo
$ hg ci -qAm '755'
reverting to rev 0
$ hg revert -a -r 0
reverting foo
$ hg st
M foo
$ hg diff --git
diff --git a/foo b/foo
old mode 100755
new mode 100644
$ cd ..