pycompat: drop the pickle import
I suspect this is what
df56e6bd37f6 meant to eliminate.
Differential Revision: https://phab.mercurial-scm.org/D12420
util: restore the util.pickle symbol
This was accidently dropped in
df56e6bd37f6, which started importing pickle
directly. That commit explicitly says it will retain it for compatibility with
external stuff though.
The unused import in pycompat isn't flagged because that module is skipped.
Just importing with a comment seemed cleaner than `import X as Y` and then
assigning to a `pickle` variable, just to avoid the pyflakes warning.
Differential Revision: https://phab.mercurial-scm.org/D12419
precheck: fix false warning about content-divergence creation
Before this patch, if we try to `hg prune` (without any successors) an
already obsoleted cset which has at least one successor, it would false
warn about new content-divergence. As we know, pruning cset without any
successors can not create any divergence.
Differential Revision: https://phab.mercurial-scm.org/D12002