tests: make tests with temporary environment setting portable With "dash" (as "/bin/sh" on Debian GNU/Linux), command execution in "ENV=val foo bar" style doesn't work as expect in test script files, if "foo" is user-defined function: it works fine, if "foo" is existing commands like "hg". 09049042ab99 introduced tests for HGPLAIN and HGPLAINEXCEPT into test-revset.t, and all of them are in such style. This patch doesn't: - add explicit unsetting for HGPLAIN and HGPLAINEXCEPT they are already introduced by 09049042ab99 - write assignment and exporting in one line "ENV=val; export ENV" for two or more environment variables in one line causes failure of test-check-code-hg.t: it is recognized as "don't export and assign at once" unfortunately.

Just exercise debugindexdot
Create a short file history including a merge.
  $ hg init t
  $ cd t
  $ echo a > a
  $ hg ci -qAm t1 -d '0 0'
  $ echo a >> a
  $ hg ci -m t2 -d '1 0'
  $ hg up -qC 0
  $ echo b >> a
  $ hg ci -m t3 -d '2 0'
  created new head
  $ HGMERGE=true hg merge -q
  $ hg ci -m merge -d '3 0'

  $ hg debugindexdot .hg/store/data/a.i
  digraph G {
  	-1 -> 0
  	0 -> 1
  	0 -> 2
  	2 -> 3
  	1 -> 3
  }

  $ cd ..