push: rework the computation of fallbackheads to be correct The previous computation tried to be smart but ended up being wrong. This was caught by phase movement test while reworking the phase discovery logic to be faster. The previous logic was failing to catch case where the pushed set was not based on a common heads (i.e. when the discovery seemed to have "over discovered" content, outside the pushed set) In the following graph, `e` is a common head and we `hg push -r f`. We need to detect `c` as a fallback heads and we previous failed to do so:: e | d f |/ c | b | a The performance impact of the change seems minimal. On the most impacted repository at hand (mozilla-try), the slowdown seems mostly mixed in the overall noise `hg push` but seems to be in the hundred of milliseconds order of magnitude. When using rust, we seems to be a bit faster, probably because we leverage more accelaratd internals. I added a couple of performance related common for further investigation later on.

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  $ rm -rf a

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  $ hg init a

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  $ cd a

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  $ echo a > a

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  $ hg ci -Am0

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  adding a

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  $ hg tag t1 # 1

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  $ hg tag --remove t1 # 2

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  $ hg co 1

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  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

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  $ hg tag -f -r0 t1

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  $ hg tags

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  tip                                3:a49829c4fc11

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  t1                                 0:f7b1eb17ad24

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Ensure that the username access fails gracefully if assumptions about the

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environment made by python do not hold.

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#if windows

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  >>> import os

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  >>> from mercurial import util

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  >>> os.environ.pop('LOGNAME', None) and None

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  >>> os.environ.pop('USER', None) and None

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  >>> os.environ.pop('LNAME', None) and None

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  >>> os.environ.pop('USERNAME', None) and None

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  >>> print(util.username())

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  None

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#endif

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  $ cd ..