test-merge-tools: introduce a "revision 4" that merges with conflict

We need conflicts to test the premerge=keep configuration.

tests/test-merge-tools.t

@@ -30,6 +30,14 b' revision 3 - simple to merge'
   $ echo "revision 3" >> f
   $ hg commit -Am "revision 3"
   created new head
+
+revision 4 - hard to merge
+
+  $ hg update 0 > /dev/null
+  $ echo "revision 4" > f
+  $ hg commit -Am "revision 4"
+  created new head
+
   $ echo "[merge-tools]" > .hg/hgrc
 
   $ beforemerge() {
@@ -832,17 +840,17 b' for Unix-like permission)'
   true.priority=1
   true.executable=cat
   # hg update -C 1
-  $ echo "revision 4" > '"; exit 1; echo "'
-  $ hg commit -Am "revision 4"
-  adding "; exit 1; echo "
-  warning: filename contains '"', which is reserved on Windows: '"; exit 1; echo "'
-  $ hg update -C 1 > /dev/null
   $ echo "revision 5" > '"; exit 1; echo "'
   $ hg commit -Am "revision 5"
   adding "; exit 1; echo "
   warning: filename contains '"', which is reserved on Windows: '"; exit 1; echo "'
+  $ hg update -C 1 > /dev/null
+  $ echo "revision 6" > '"; exit 1; echo "'
+  $ hg commit -Am "revision 6"
+  adding "; exit 1; echo "
+  warning: filename contains '"', which is reserved on Windows: '"; exit 1; echo "'
   created new head
-  $ hg merge --config merge-tools.true.executable="true" -r 4
+  $ hg merge --config merge-tools.true.executable="true" -r 5
   merging "; exit 1; echo "
   0 files updated, 1 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)