Issue a warning if "-r ." is used with two working directory parents.
Rationale for not aborting instead:
The first parent is usually more important as it is the local branch
during a merge and commands like 'hg diff' and 'hg diff -r.' behave still
identically (except for the warning of course).
Added a test for log -r. with one and two parents.
adding foo
>>> two diffs showing three added lines <<<
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@ hello world
+
hello world
+
goodbye world
+
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@ hello world
+
hello world
+
goodbye world
+
>>> no diffs <<<
>>> four diffs showing added space first on the first line <<<
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
-hello world
+ hello world
goodbye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
-hello world
+ hello world
goodbye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
-hello world
+ hello world
goodbye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
-hello world
+ hello world
goodbye world
>>> two diffs showing space appended to the first line <<<
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
-hello world
+hello world
goodbye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
-hello world
+hello world
goodbye world
>>> no diffs <<<
>>> four diffs showing space inserted into "goodbye" <<<
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
hello world
-goodbye world
+good bye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
hello world
-goodbye world
+good bye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
hello world
-goodbye world
+good bye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
hello world
-goodbye world
+good bye world
>>> two diffs showing changed whitespace amount in the last line <<<
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
hello world
-goodbye world
+goodbye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@ hello world
hello world
-goodbye world
+goodbye world
>>> no diffs <<<
>>> four diffs showing added blank line w/horizontal space <<<
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@ hello world
hello world
+
goodbye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@ hello world
hello world
+
goodbye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@ hello world
hello world
+
goodbye world
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@ hello world
hello world
+
goodbye world