hgignore: fix .err matching patterns
We don't want to ignore .err file outside of the 'tests/' directory.
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Evolve Commands Reference
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.. highlight:: none
amend
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.. hghelp:: amend
evolve
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.. hghelp:: evolve
fold
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.. hghelp:: fold
metaedit
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.. hghelp:: metaedit
next
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.. hghelp:: next
obslog
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.. hghelp:: obslog
pdiff
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.. hghelp:: pdiff
previous
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.. hghelp:: previous
prune
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.. hghelp:: prune
pstatus
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.. hghelp:: pstatus
split
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.. hghelp:: split
touch
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.. hghelp:: touch
uncommit
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.. hghelp:: uncommit