hg is gone after computer is powered off

[Greg Ward]

On Fri, Nov 12, 2010 at 1:48 AM, Ma, Xiangjiang
<maxiangjiang at cornell.edu> wrote:
> Hi,
>
> I used cygwin on Vista.  I have enjoyed hg for many months until today when
> hg is gone.  Following is the error:
>
> $ hg diff vimim.vim
> ** unknown exception encountered, details follow
> ** report bug details to http://mercurial.selenic.com/bts/
> ** or mercurial at selenic.com
> ** Python 2.6.5 (r265:79063, Jun 12 2010, 17:07:01) [GCC 4.3.4 20090804
> (release) 1]
> ** Mercurial Distributed SCM (version 1.5.4)
> ** Extensions loaded:
> Traceback (most recent call last):
[...]
>     self._node = self._repo.lookup(changeid)
>   File "/usr/lib/python2.6/site-packages/mercurial/localrepo.py", line 440, in lookup
>     if key in self.tags():
>   File "/usr/lib/python2.6/site-packages/mercurial/localrepo.py", line 250, in tags
>     (self._tags, self._tagtypes) = self._findtags()
>   File "/usr/lib/python2.6/site-packages/mercurial/localrepo.py", line 271, in _findtags
>     tags_.findglobaltags(self.ui, self, alltags, tagtypes)
>   File "/usr/lib/python2.6/site-packages/mercurial/tags.py", line 96, in findglobaltags2
>     _writetagcache(ui, repo, heads, tagfnode, alltags)
>   File "/usr/lib/python2.6/site-packages/mercurial/tags.py", line 320, in _writetagcache
>     'trying to write nullid to tag cache' AssertionError: trying to write nullid to tag cache

Uh-oh!

First thing to try: upgrade to Mercurial 1.7 and see if you still get
the same error.  I suspect you will, but 1.5.4 is a bit old.

Next thing to try: "hg verify".  You *might* have a corrupt repository.

Oh yeah, also try running "hg tags --debug".

Third thing to try: show us the contents of .hgtags *on all heads*.  E.g. run

  hg heads -tq

to get the changeset ID of every head.  Then, for each changeset ID
that prints, run

  hg cat -r <cset> .hgtags > .hgtags-<cset>

If there are only a couple of such files, and they are not too big,
include them in your email.  If not, can you put a tar or zip file
somewhere we can download it from?  Something might be wrong with one
of those files which is confusing Mercurial.

Greg