changegroup: store old heads as a set Previously, the "oldheads" variable was a list. On a repository at Mozilla with 46,492 heads, profiling revealed that list membership testing was dominating execution time of applying small changegroups. This patch converts the list of old heads to a set. This makes membership testing significantly faster. On the aforementioned repository with 46,492 heads: $ hg unbundle <file with 1 changeset> before: 18.535s wall after: 1.303s Consumers of this variable only check for truthiness (`if oldheads`), length (`len(oldheads)`), and (most importantly) item membership (`h not in oldheads` - which occurs twice). So, the change to a set should be safe and suitable for stable. The practical effect of this change is that changegroup application and related operations (like `hg push`) no longer exhibit an O(n^2) CPU explosion as the number of heads grows.

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# Disable the $CAP wire protocol capability.

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if test -z "$CAP"

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then

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    echo "CAP environment variable not set."

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fi

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cat > notcapable-$CAP.py << EOF

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from mercurial import extensions, peer, localrepo

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def extsetup():

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    extensions.wrapfunction(peer.peerrepository, 'capable', wrapcapable)

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    extensions.wrapfunction(localrepo.localrepository, 'peer', wrappeer)

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def wrapcapable(orig, self, name, *args, **kwargs):

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    if name in '$CAP'.split(' '):

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        return False

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    return orig(self, name, *args, **kwargs)

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def wrappeer(orig, self):

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    # Since we're disabling some newer features, we need to make sure local

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    # repos add in the legacy features again.

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    return localrepo.locallegacypeer(self)

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EOF

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echo '[extensions]' >> $HGRCPATH

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echo "notcapable-$CAP = `pwd`/notcapable-$CAP.py" >> $HGRCPATH