copies: rewrite copy detection for non-merge users
The existing copy detection API was designed with merge in mind and
was ill-suited for doing status/diff. The new pathcopies
implementation gives more accurate, easier to use results for
comparing two revisions, and is much simpler to understand.
Test notes:
- test-mv-cp-st.t results finds more renames in the reverse direction now
- test-mq-merge.t was always wrong and duplicated a copy in diff that
was already present in one of the parent revisions
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ hg update 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo This is file c1 > c
$ hg add c
$ hg commit -m "commit #2"
created new head
$ hg merge 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ rm b
$ echo This is file c22 > c
$ hg commit -m "commit #3"