test-copies: add 3 new files with their own content

The new `p`, `q` and `r` file mirror the `a`, `b` and `h` but with different
content for each files. This will be used to create "mirror" test case that
involve actual merge happening.

For now, we only add the file to keep patches small and easier to review.

Differential Revision: https://phab.mercurial-scm.org/D10053

tests/test-copies-chain-merge.t

@@ -75,10 +75,16 b' Add some linear rename initialy'
   $ cp ../same-content.txt a
   $ cp ../same-content.txt b
   $ cp ../same-content.txt h
+  $ echo "original content for P" > p
+  $ echo "original content for Q" > q
+  $ echo "original content for R" > r
   $ hg ci -Am 'i-0 initial commit: a b h'
   adding a
   adding b
   adding h
+  adding p
+  adding q
+  adding r
   $ hg mv a c
   $ hg ci -Am 'i-1: a -move-> c'
   $ hg mv c d
@@ -652,7 +658,7 b' rename information actually conflict wit'
   $ case_desc="simple merge - C side: d is the results of renames then deleted, H side: d is result of another rename (same content as the other branch)"
 
   $ hg up 'desc("i-0")'
-  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  6 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg mv b d
   $ hg ci -m "h-1: b -(move)-> d"
   created new head
@@ -1228,6 +1234,9 b' We upgrade a repository that is not usin'
   added      : a, ;
   added      : b, ;
   added      : h, ;
+  added      : p, ;
+  added      : q, ;
+  added      : r, ;
 
   $ for rev in `hg log --rev 'all()' -T '{rev}\n'`; do
   >     case_id=`hg log -r $rev -T '{word(0, desc, ":")}\n'`
@@ -1237,11 +1246,14 b' We upgrade a repository that is not usin'
   > done
   ##### revision "i-0 initial commit" #####
   1 sidedata entries
-   entry-0014 size 34
-    '\x00\x00\x00\x03\x04\x00\x00\x00\x01\x00\x00\x00\x00\x04\x00\x00\x00\x02\x00\x00\x00\x00\x04\x00\x00\x00\x03\x00\x00\x00\x00abh'
+   entry-0014 size 64
+    '\x00\x00\x00\x06\x04\x00\x00\x00\x01\x00\x00\x00\x00\x04\x00\x00\x00\x02\x00\x00\x00\x00\x04\x00\x00\x00\x03\x00\x00\x00\x00\x04\x00\x00\x00\x04\x00\x00\x00\x00\x04\x00\x00\x00\x05\x00\x00\x00\x00\x04\x00\x00\x00\x06\x00\x00\x00\x00abhpqr'
   added      : a, ;
   added      : b, ;
   added      : h, ;
+  added      : p, ;
+  added      : q, ;
+  added      : r, ;
   ##### revision "i-1" #####
   1 sidedata entries
    entry-0014 size 24