tests/test-username-newline.t

repo: rephrase the "missing requirement" error message

Unknown requirements will now be reported as:
  abort: repository requires features unknown to this Mercurial: largefiles!
  (see http://mercurial.selenic.com/wiki/MissingRequirement for more information)

Some features of this phrasing:
* avoid double ':' in abort message
* make it more clear who requires and knows what
* don't quote the requirement names - it is not something the user entered or
  need the exact spelling of ... and it is "identifiers" that are unambiguous
  anyway
* remove double hint by removing "(upgrade Mercurial)" comment
* don't mention upgrading Mercurial without mentioning enabling the feature -
  instead, just refer to wiki page for both
* don't just talk about "details", talk about "more information"

  $ hg init
  $ touch a

  $ unset HGUSER
  $ echo "[ui]" >> .hg/hgrc
  $ echo "username= foo" >> .hg/hgrc
  $ echo "          bar1" >> .hg/hgrc

  $ hg ci -Am m
  adding a
  abort: username 'foo\nbar1' contains a newline
  
  [255]
  $ rm .hg/hgrc

  $ HGUSER=`(echo foo; echo bar2)` hg ci -Am m
  abort: username 'foo\nbar2' contains a newline
  
  [255]
  $ hg ci -Am m -u "`(echo foo; echo bar3)`"
  transaction abort!
  rollback completed
  abort: username 'foo\nbar3' contains a newline!
  [255]