cmdutil: normalize log message eols when reading from file
This will be necessary once util.readfile() operates in binary mode. While
changelog.add() already normalizes the message, doing so in logmessage() is
required as ui.edit() or others expect messages with LF only.
Simple commands:
$ echo foo
foo
$ printf 'oh no'
oh no (no-eol)
$ printf 'bar\nbaz\n' | cat
bar
baz
Multi-line command:
$ foo() {
> echo bar
> }
$ foo
bar
Regular expressions:
$ echo foobarbaz
foobar.* (re)
$ echo barbazquux
.*quux.* (re)
Globs:
$ printf '* \\foobarbaz {10}\n'
\* \\fo?bar* {10} (glob)
Literal match ending in " (re)":
$ echo 'foo (re)'
foo (re)
Exit code:
$ (exit 1)
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