commitctx: extract copy information encoding into extra into commit.py
The encoding of copy information into extra has multiple subcases and become
quite complicated (eg: empty list can be explicitly or implicitly stored for
example). In addition, it is niche experimental feature since as it affect the
hash, it is only suitable for user who don't mercurial for storage server side
(ie: Google).
Having this complexity part of the changelog will get in the way of further
cleanup. We could have to either move more of that logic into the changelog or
to move or extract more of the logic at the higher level. We take the second
approach and start gather logic in dedicated function in commit.py.
$ hg init a
$ cd a
$ echo 123 > a
$ hg add a
$ hg commit -m "a" -u a
$ cd ..
$ hg init b
$ cd b
$ echo 321 > b
$ hg add b
$ hg commit -m "b" -u b
$ hg pull ../a
pulling from ../a
searching for changes
abort: repository is unrelated
[255]
$ hg pull -f ../a
pulling from ../a
searching for changes
warning: repository is unrelated
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 9a79c33a9db3
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg heads
changeset: 1:9a79c33a9db3
tag: tip
parent: -1:000000000000
user: a
date: Thu Jan 01 00:00:00 1970 +0000
summary: a
changeset: 0:01f8062b2de5
user: b
date: Thu Jan 01 00:00:00 1970 +0000
summary: b
$ cd ..