contrib/editmergeps.ps1

chg: set CHGHG before connecting to command server

cf4d2f31 (!523) changed chg to set `CHGHG` itself when spawning a new command
server, in order to ensure that the path to the `hg` executable would be checked
during server validation. (This is useful when chg is built with `HGPATHREL`).

However, that change broke chg because it failed to set `CHGHG` before trying
to connect to an existing command server. This means that if `CHGHG` is not
present in the environment, chg will always spawn a new command server, entirely
negating the point of chg.

This breakage wasn't initially caught because of the difficulty of writing
automated tests with the `HGPATHREL` feature enabled, which meant the change
was only tested manually to make sure that it fixed the problem with `HGPATHREL`
that prompted the change.

In practice, this functionality is only really useful when chg is built with
`HGPATHREL`, so I considered wrapping it in an `#ifdef` to preserve the old
behavior by default. However, this makes it hard to write tests since one would
have to explicitly set `HGPATHREL=1` when running `run-tests.py` (which is why
the original change lacked tests). It would be great if there were a way of
testing features that are gated behind conditional compilation.

# A simple script for opening merge conflicts in editor
# A loose translation of contrib/editmerge to powershell
# Please make sure that both editmergeps.bat and editmerge.ps1 are available
# via %PATH% and use the following Mercurial settings to enable it
#
# [ui]
# editmergeps
# editmergeps.args=$output
# editmergeps.check=changed
# editmergeps.premerge=keep

$file=$args[0]

function Get-Lines
{
  Select-String "^<<<<<<" $file | % {"$($_.LineNumber)"}
}

$ed = $Env:HGEDITOR;
if ($ed -eq $nil)
{
  $ed = $Env:VISUAL;
}
if ($ed -eq $nil)
{
  $ed = $Env:EDITOR;
}
if ($ed -eq $nil)
{
  $ed = $(hg showconfig ui.editor);
}
if ($ed -eq $nil)
{
  Write-Error "merge failed - unable to find editor"
  exit 1
}

if (($ed -eq "vim") -or ($ed -eq "emacs") -or `
    ($ed -eq "nano") -or ($ed -eq "notepad++"))
{
  $lines = Get-Lines
  $firstline = if ($lines.Length -gt 0) { $lines[0] } else { $nil }
  $previousline = $nil;


  # open the editor to the first conflict until there are no more
  # or the user stops editing the file
  while (($firstline -ne $nil) -and ($firstline -ne $previousline))
  {
    if ($ed -eq "notepad++")
    {
        $linearg = "-n$firstline"
    }
    else
    {
        $linearg = "+$firstline"
    }

    Start-Process -Wait -NoNewWindow $ed $linearg,$file
    $previousline = $firstline
    $lines = Get-Lines
    $firstline = if ($lines.Length -gt 0) { $lines[0] } else { $nil }
  }
}
else
{
  & "$ed" $file
}

$conflicts=Get-Lines
if ($conflicts.Length -ne 0)
{
  Write-Output "merge failed - resolve the conflicts (line $conflicts) then use 'hg resolve --mark'"
  exit 1
}

exit 0