Fix hg clone race with writer
Most read operations in hg don't need locks because we order reads and
writes for consistency. Clone is an exception to this as we're copying
entire file histories and could end up with more file history copied
than we have commits.
For now, make clone take a lock on the source repo. Non-hardlinked
clone should eventually be changed to use lockless pull.
+ hg init
+ hg add a
+ hg commit -m 1 -d 0 0
+ hg status
+ hg copy a b
+ hg status
A b
+ hg --debug commit -m 2 -d 0 0
b
b: copy a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3
+ hg history
changeset: 1:3b5b84850bbe
tag: tip
user: test
date: Thu Jan 1 00:00:00 1970
summary: 2
changeset: 0:c19d34741b0a
user: test
date: Thu Jan 1 00:00:00 1970
summary: 1
+ hg log a
changeset: 0:c19d34741b0a
user: test
date: Thu Jan 1 00:00:00 1970
summary: 1
566e338d09a089ba737c21e0d3759980 .hg/data/b.d
3268d2f51b2d2d423ff01b59eb6fbb14 bsum
70909ca2ecf494c71e9184b445e040ee asum
+ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
2 files, 2 changesets, 2 total revisions