transaction: quietly rollback if no other changes than temporary files
If no actual change have been made, we don't really need to roll them back. We
only have to cleanup some temporary files and it seems reasonable to do that
quietly.
This will help us to use the transaction in wider context¹ without impacting the
user experience.
[1] as in Python context managers that lives longer.
$ cat > bundle2.py << EOF
> """A small extension to test bundle2 pushback parts.
> Current bundle2 implementation doesn't provide a way to generate those
> parts, so they must be created by extensions.
> """
> from mercurial import bundle2, exchange, pushkey, util
> def _newhandlechangegroup(op, inpart):
> """This function wraps the changegroup part handler for getbundle.
> It issues an additional pushkey part to send a new
> bookmark back to the client"""
> result = bundle2.handlechangegroup(op, inpart)
> if b'pushback' in op.reply.capabilities:
> params = {b'namespace': b'bookmarks',
> b'key': b'new-server-mark',
> b'old': b'',
> b'new': b'tip'}
> encodedparams = [(k, pushkey.encode(v))
> for (k, v) in params.items()]
> op.reply.newpart(b'pushkey', mandatoryparams=encodedparams)
> else:
> op.reply.newpart(b'output', data=b'pushback not enabled')
> return result
> _newhandlechangegroup.params = bundle2.handlechangegroup.params
> bundle2.parthandlermapping[b'changegroup'] = _newhandlechangegroup
> EOF
$ cat >> $HGRCPATH <<EOF
> [ui]
> username = nobody <no.reply@example.com>
>
> [alias]
> tglog = log -G -T "{desc} [{phase}:{node|short}]"
> EOF
Set up server repository
$ hg init server
$ cd server
$ echo c0 > f0
$ hg commit -Am 0
adding f0
Set up client repository
$ cd ..
$ hg clone ssh://user@dummy/server client -q
$ cd client
Enable extension
$ cat >> $HGRCPATH <<EOF
> [extensions]
> bundle2=$TESTTMP/bundle2.py
> EOF
Without config
$ cd ../client
$ echo c1 > f1
$ hg commit -Am 1
adding f1
$ hg push
pushing to ssh://user@dummy/server
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files
remote: pushback not enabled
$ hg bookmark
no bookmarks set
$ cd ../server
$ hg tglog
o 1 [public:2b9c7234e035]
|
@ 0 [public:6cee5c8f3e5b]
With config
$ cd ../client
$ echo '[experimental]' >> .hg/hgrc
$ echo 'bundle2.pushback = True' >> .hg/hgrc
$ echo c2 > f2
$ hg commit -Am 2
adding f2
$ hg push
pushing to ssh://user@dummy/server
searching for changes
remote: adding changesets
remote: adding manifests
remote: adding file changes
remote: added 1 changesets with 1 changes to 1 files
$ hg bookmark
new-server-mark 2:0a76dfb2e179
$ cd ../server
$ hg tglog
o 2 [public:0a76dfb2e179]
|
o 1 [public:2b9c7234e035]
|
@ 0 [public:6cee5c8f3e5b]