bisect: avoid copying ancestor list for non-merge commits During a bisection, hg needs to compute a list of all ancestors for every candidate commit. This is accomplished via a bottom-up traversal of the set of candidates, during which each revision's ancestor list is populated using the ancestor list of its parent(s). Previously, this involved copying the entire list, which could be very long in if the bisection range was large. To help improve this, we can observe that each candidate commit is visited exactly once, at which point its ancestor list is copied into its children's lists and then dropped. In the case of non-merge commits, a commit's ancestor list consists exactly of its parent's list plus itself. This means that we can trivially reuse the parent's existing list for one of its non-merge children, which avoids copying entirely if that commit is the parent's only child. This makes bisections over linear ranges of commits much faster. During some informal testing in the large publicly-available `mozilla-central` repository, this noticeably sped up bisections over large ranges of history: Setup: $ cd mozilla-central $ hg bisect --reset $ hg bisect --good 0 $ hg log -r tip -T '{rev}\n' 628417 Test: $ time hg bisect --bad tip --noupdate Before: real 3m35.927s user 3m35.553s sys 0m0.319s After: real 1m41.142s user 1m40.810s sys 0m0.285s

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cHg

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===

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A fast client for Mercurial command server running on Unix.

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Install:

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 $ make

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 $ make install

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Usage:

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 $ chg help                 # show help of Mercurial

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 $ alias hg=chg             # replace hg command

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 $ chg --kill-chg-daemon    # terminate background server

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Environment variables:

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Although cHg tries to update environment variables, some of them cannot be

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changed after spawning the server. The following variables are specially

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handled:

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 * configuration files are reloaded automatically by default.

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 * CHGHG or HG specifies the path to the hg executable spawned as the

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   background command server.

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The following variables are available for testing:

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 * CHGDEBUG enables debug messages.

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 * CHGSOCKNAME specifies the socket path of the background cmdserver.

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 * CHGTIMEOUT specifies how many seconds chg will wait before giving up

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   connecting to a cmdserver. If it is 0, chg will wait forever. Default: 60

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Build environment variables:

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 * HGPATH: the path to the hg executable to call when CHGHG and HG are not set,

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   instead of "hg"

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 * HGPATHREL=1: when CHGHG and HG are not set, the hg executable will be ./hg

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   relative to the chg executable. Only works on linux, falls back to "hg"

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   otherwise.