tests/test-alias.t

29086:fe50341de1ff

   update        update working directory (or switch revisions)
  
  (use "hg help" for the full list of commands or "hg -v" for details)
  [255]

This should show id:

  $ hg --config alias.log='id' log
  000000000000 tip

29087:ad1bdea43965

   update        update working directory (or switch revisions)
  
  (use "hg help" for the full list of commands or "hg -v" for details)
  [255]

environment variable changes in alias commands

  $ cat > $TESTTMP/setcount.py <<EOF
  > import os
  > def uisetup(ui):
  >     os.environ['COUNT'] = '2'
  > EOF

  $ cat >> $HGRCPATH <<'EOF'
  > [extensions]
  > setcount = $TESTTMP/setcount.py
  > [alias]
  > showcount = log -T "$COUNT\n" -r .
  > EOF

  $ COUNT=1 hg showcount
  2

This should show id:

  $ hg --config alias.log='id' log
  000000000000 tip