rebase: do not invent successor to skipped changeset
When rebase results in an empty a changeset it is "skipped" and no related
changeset is created at all. When we added obsolescence support to rebase (in
fc2a6114f0a0) it seemed a good idea to use its parent successor as the
successors for such dropped changesets. (see old version of the altered test).
This option was chosen because it seems a good way to hint about were the
dropped changeset "intended" to be. Such hint would have been used by automatic
evolution mechanism to rebase potential unstable children.
However, field testing of this version are not conclusive. It very often leads
to the creation of (totally unfounded) evolution divergence. This changeset
changes this behavior and mark skipped changesets as pruned (obsolete without
successors). This prevents the issue and seems semantically better probably a
win for obsolescence reading tool.
See example bellow for details:
User Babar has five changesets of interest:
- O, its current base of development.
- U, the new upstream
- A and C, some development changesets
- B another development changeset independent from A
O - A - B - C
\
U
Babar decides that B is more critical than the A and C and rebase it first
$ hg rebase --rev B --dest U
B is now obsolete (in lower case bellow). Rebase result, B', is its
successors.(note, C is unstable)
O - A - b - C
\
U - B'
Babar is now done with B', and want to rebase the rest of its history:
$ hg rebase --source A --dest B'
hg rebase process A, B and C. B is skipped as all its changes are already contained
in B'.
O - U - B' - A' - C'
Babar have the expected result graph wise, obsolescence marker are as follow:
B -> B' (from first rebase)
A -> A' (from second rebase)
C -> C' (from second rebase)
B -> ?? (from second rebase)
Before this changeset, the last marker is `B -> A'`. This cause two issues:
- This is semantically wrong. B have nothing to do with A'
- B has now two successors sets: (B',) and (A',). We detect a divergent
rewriting. The B' and A' are reported as "divergent" to Babar, confusion
ensues. In addition such divergent situation (divergent changeset are children
to each other) is tricky to solve.
With this changeset the last marker is `B -> ΓΈ`:
- This is semantically better.
- B has a single successors set (B',)
This scenario is added to the tests suite.
$ hg init repo
$ cd repo
$ hg init subrepo
$ echo a > subrepo/a
$ hg -R subrepo ci -Am adda
adding a
$ echo 'subrepo = subrepo' > .hgsub
$ hg ci -Am addsubrepo
adding .hgsub
$ echo b > subrepo/b
$ hg -R subrepo ci -Am addb
adding b
$ hg ci -m updatedsub
ignore blanklines in .hgsubstate
>>> file('.hgsubstate', 'wb').write('\n\n \t \n \n')
$ hg st --subrepos
M .hgsubstate
$ hg revert -qC .hgsubstate
abort more gracefully on .hgsubstate parsing error
$ cp .hgsubstate .hgsubstate.old
>>> file('.hgsubstate', 'wb').write('\ninvalid')
$ hg st --subrepos
abort: invalid subrepository revision specifier in .hgsubstate line 2
[255]
$ mv .hgsubstate.old .hgsubstate
delete .hgsub and revert it
$ rm .hgsub
$ hg revert .hgsub
warning: subrepo spec file .hgsub not found
warning: subrepo spec file .hgsub not found
delete .hgsubstate and revert it
$ rm .hgsubstate
$ hg revert .hgsubstate
delete .hgsub and update
$ rm .hgsub
$ hg up 0
warning: subrepo spec file .hgsub not found
warning: subrepo spec file .hgsub not found
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg st
warning: subrepo spec file .hgsub not found
! .hgsub
$ ls subrepo
a
delete .hgsubstate and update
$ hg up -C
warning: subrepo spec file .hgsub not found
warning: subrepo spec file .hgsub not found
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm .hgsubstate
$ hg up 0
remote changed .hgsubstate which local deleted
use (c)hanged version or leave (d)eleted? c
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg st
$ ls subrepo
a
$ cd ..