contrib/editmerge

debugcommands: introduce actions to perform deterministic reads

"readavailable" is useful as a debugging device to see what data is
available on a pipe. But the mechanism isn't deterministic because
what's available on a pipe is highly conditional on timing, system
load, OS behavior, etc. This makes it not suitable for tests.

We introduce "ereadline," "read," and "eread" for performing
deterministic I/O operations (at least on blocking file descriptors).

We stop short of converting existing consumers of "readavailable"
in tests because we're working out race conditions and deadlocks
on Windows. But the goal is to eventually move tests away from
"readavailable" to these new APIs.

Differential Revision: https://phab.mercurial-scm.org/D2720

#!/usr/bin/env bash
# A simple script for opening merge conflicts in the editor.
# Use the following Mercurial settings to enable it.
#
# [ui]
# merge = editmerge
#
# [merge-tools]
# editmerge.args=$output
# editmerge.check=changed
# editmerge.premerge=keep

FILE="$1"

getlines() {
  grep -n "^<<<<<<" "$FILE" | cut -f1 -d:
}

# editor preference loosely based on https://mercurial-scm.org/wiki/editor
# hg showconfig is at the bottom though, since it's slow to run (0.15 seconds)
ED="$HGEDITOR"
if [ "$ED" = "" ] ; then
  ED="$VISUAL"
fi
if [ "$ED" = "" ] ; then
  ED="$EDITOR"
fi
if [ "$ED" = "" ] ; then
  ED="$(hg showconfig ui.editor)"
fi
if [ "$ED" = "" ] ; then
  echo "merge failed - unable to find editor"
  exit 1
fi

if [ "$ED" = "emacs" ] || [ "$ED" = "nano" ] || [ "$ED" = "vim" ] ; then
  FIRSTLINE="$(getlines | head -n 1)"
  PREVIOUSLINE=""

  # open the editor to the first conflict until there are no more
  # or the user stops editing the file
  while [ ! "$FIRSTLINE" = "" ] && [ ! "$FIRSTLINE" = "$PREVIOUSLINE" ] ; do
    $ED "+$FIRSTLINE" "$FILE"
    PREVIOUSLINE="$FIRSTLINE"
    FIRSTLINE="$(getlines | head -n 1)"
  done
else
  $ED "$FILE"
fi

# get the line numbers of the remaining conflicts
CONFLICTS="$(getlines | sed ':a;N;$!ba;s/\n/, /g')"
if [ ! "$CONFLICTS" = "" ] ; then
  echo "merge failed - resolve the conflicts (line $CONFLICTS) then use 'hg resolve --mark'"
  exit 1
fi

exit 0