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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Mercurial

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=========

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Mercurial is a fast, easy to use, distributed revision control tool

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for software developers.

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Basic install:

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 $ make            # see install targets

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 $ make install    # do a system-wide install

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 $ hg debuginstall # sanity-check setup

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 $ hg              # see help

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Running without installing:

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 $ make local      # build for inplace usage

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 $ ./hg --version  # should show the latest version

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See https://mercurial-scm.org/ for detailed installation

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instructions, platform-specific notes, and Mercurial user information.