Store empty (default) branch in branch cache, too.
Operations on this branch don't work otherwise.
Reading branches.cache had to be adjusted to allow an empty label.
Adjusted reading of the cache tip for symmetry, no functional change here.
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