tests: demonstrate bug in `hg fix` with incorrectly dirty working copy

If the parent commit needs formatting but the working copy already has
the correct formatting, then the working copy will be reported as
modified even though it's clean (because the size in the dirstate is
incorrect). Because the bug only occurs when the size changes, I
modified the formatter used in the test case to remove repeated
spaces.

Differential Revision: https://phab.mercurial-scm.org/D11208

tests/test-fix.t

@@ -3,6 +3,7 b' approximates the behavior of code format'
 
   $ UPPERCASEPY="$TESTTMP/uppercase.py"
   $ cat > $UPPERCASEPY <<EOF
+  > import re
   > import sys
   > from mercurial.utils.procutil import setbinary
   > setbinary(sys.stdin)
@@ -10,16 +11,18 b' approximates the behavior of code format'
   > stdin = getattr(sys.stdin, 'buffer', sys.stdin)
   > stdout = getattr(sys.stdout, 'buffer', sys.stdout)
   > lines = set()
+  > def format(text):
+  >   return re.sub(b' +', b' ', text.upper())
   > for arg in sys.argv[1:]:
   >   if arg == 'all':
-  >     stdout.write(stdin.read().upper())
+  >     stdout.write(format(stdin.read()))
   >     sys.exit(0)
   >   else:
   >     first, last = arg.split('-')
   >     lines.update(range(int(first), int(last) + 1))
   > for i, line in enumerate(stdin.readlines()):
   >   if i + 1 in lines:
-  >     stdout.write(line.upper())
+  >     stdout.write(format(line))
   >   else:
   >     stdout.write(line)
   > EOF
@@ -354,6 +357,24 b' Fixing the working directory should stil'
 
   $ cd ..
 
+Test that the working copy is reported clean if formatting of the parent makes
+it clean.
+  $ hg init wc-already-formatted
+  $ cd wc-already-formatted
+
+  $ printf "hello   world\n" > hello.whole
+  $ hg commit -Am initial
+  adding hello.whole
+  $ hg fix -w *
+  $ hg st
+  M hello.whole
+  $ hg fix -s . *
+  $ hg st
+  M hello.whole (known-bad-output !)
+  $ hg diff
+
+  $ cd ..
+
 Test the effect of fixing the working directory for each possible status, with
 and without providing explicit file arguments.