Comment 12 for bug 772935

Yay!

I investigated a bit further, and it looks like a bug with how this branch was
stacked. Specifically:

1) The current lp:lightdm branch has this in branch.conf:
stacked_on_location = ""
parent_location = ../../../~robert-ancell/lightdm/trunk/

That hints that it used to be a stacked branch, and it used to be stacked on robert-ancell's branch.

2) I investigated, and ~robert-ancell/lightdm/trunk *does* have the text revision that was missing in lp:lightdm. Though potentially you filled it in manually, and I got to the party late.

3) The missing text is from a fairly old revision (from 2010).

So my guess is that the text was present in ~robert-ancell and the ~lightdm-team branch was stacked on it, so it didn't copy that text. When the ~lightdm-team branch was later promoted to development focus and then unstacked, it didn't get all of the history filled in properly.

4) I grabbed a copy of "lp:lightdm" while it was broken using hitchhiker. I was unable to branch it to another location. If I edited ".bzr/branch/branch.conf" to change it to:
stacked_on_location = "bzr+ssh://bazaar.launchpad.net/~robert-ancell/lightdm/trunk"

I was then able to "bzr branch lightdm xxx"

So my guess is that the branch was unstacked by just removing the
stacking_location, rather than "bzr reconfigure --unstacked". Which leaves us
with a branch that is missing some of its history, and doesn't have a reference
for where to find that history.