Returns lines changed for paths specified as arguments correctly.

This fixes issue 1569. hg churn <path> now returns only the number
of lines changed in the path, if the path is specified by filtering
files through a match filter at the changeset level. test-churn
has been updated to take care of this issue.

hgext/churn.py

@@ -21,9 +21,10 b' def maketemplater(ui, repo, tmpl):'
     t.use_template(tmpl)
     return t
 
-def changedlines(ui, repo, ctx1, ctx2):
+def changedlines(ui, repo, ctx1, ctx2, fns):
     lines = 0
-    diff = ''.join(patch.diff(repo, ctx1.node(), ctx2.node()))
+    fmatch = cmdutil.match(repo, pats=fns)
+    diff = ''.join(patch.diff(repo, ctx1.node(), ctx2.node(), fmatch))
     for l in diff.split('\n'):
         if (l.startswith("+") and not l.startswith("+++ ") or
             l.startswith("-") and not l.startswith("--- ")):
@@ -71,7 +72,7 b' def countrate(ui, repo, amap, *pats, **o'
                 continue
 
             ctx1 = parents[0]
-            lines = changedlines(ui, repo, ctx1, ctx)
+            lines = changedlines(ui, repo, ctx1, ctx, fns)
             rate[key] = rate.get(key, 0) + lines
 
         if opts.get('progress'):

tests/test-churn

@@ -20,7 +20,15 b' echo c > c'
 hg ci -m changeca -u user3 -d 12:00 a
 hg ci -m changecb -u user3 -d 12:15 b
 hg ci -Am addc -u user3 -d 12:30
+mkdir -p d/e
+echo abc > d/e/f1.txt
+hg ci -Am "add d/e/f1.txt" -u user1 -d 12:45 d/e/f1.txt
+mkdir -p d/g
+echo def > d/g/f2.txt
+hg ci -Am "add d/g/f2.txt" -u user1 -d 13:00 d/g/f2.txt
 
+echo % churn separate directories
+hg churn d/e
 echo % churn all
 hg churn
 echo % churn up to rev 2

tests/test-churn.out

@@ -2,22 +2,25 b''
 adding a
 adding b
 adding c
+% churn separate directories
+user1      1 ***************************************************************
 % churn all
 user3      3 ***************************************************************
+user1      3 ***************************************************************
 user2      2 ******************************************
-user1      1 *********************
 % churn up to rev 2
 user2      2 ***************************************************************
 user1      1 *******************************
 % churn with aliases
 alias3      3 **************************************************************
+alias1      3 **************************************************************
 user2       2 *****************************************
-alias1      1 ********************
 % churn with column specifier
 user3      3 ***********************
+user1      3 ***********************
 user2      2 ***************
-user1      1 *******
 % churn by hour
-06      1 **********************
-09      2 ********************************************
-12      3 ******************************************************************
+06      1 ****************
+09      2 *********************************
+12      4 ******************************************************************
+13      1 ****************