GNU diff is the reference for all of these results.
Prepare tests:
$ echo '[alias]' >> $HGRCPATH
$ echo 'ndiff = diff --nodates' >> $HGRCPATH
$ hg init
$ printf 'hello world\ngoodbye world\n' >foo
$ hg ci -Amfoo -ufoo
adding foo
Test added blank lines:
$ printf '\nhello world\n\ngoodbye world\n\n' >foo
>>> two diffs showing three added lines <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@
+
hello world
+
goodbye world
+
$ hg ndiff -b
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@
+
hello world
+
goodbye world
+
>>> no diffs <<<
$ hg ndiff -B
$ hg ndiff -Bb
Test added horizontal space first on a line():
$ printf '\t hello world\ngoodbye world\n' >foo
>>> four diffs showing added space first on the first line <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
+ hello world
goodbye world
$ hg ndiff -b
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
+ hello world
goodbye world
$ hg ndiff -B
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
+ hello world
goodbye world
$ hg ndiff -Bb
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
+ hello world
goodbye world
Test added horizontal space last on a line:
$ printf 'hello world\t \ngoodbye world\n' >foo
>>> two diffs showing space appended to the first line <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
+hello world
goodbye world
$ hg ndiff -B
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
+hello world
goodbye world
>>> no diffs <<<
$ hg ndiff -b
$ hg ndiff -Bb
Test added horizontal space in the middle of a word:
$ printf 'hello world\ngood bye world\n' >foo
>>> four diffs showing space inserted into "goodbye" <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
hello world
-goodbye world
+good bye world
$ hg ndiff -B
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
hello world
-goodbye world
+good bye world
$ hg ndiff -b
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
hello world
-goodbye world
+good bye world
$ hg ndiff -Bb
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
hello world
-goodbye world
+good bye world
Test increased horizontal whitespace amount:
$ printf 'hello world\ngoodbye\t\t \tworld\n' >foo
>>> two diffs showing changed whitespace amount in the last line <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
hello world
-goodbye world
+goodbye world
$ hg ndiff -B
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
hello world
-goodbye world
+goodbye world
>>> no diffs <<<
$ hg ndiff -b
$ hg ndiff -Bb
Test added blank line with horizontal whitespace:
$ printf 'hello world\n \t\ngoodbye world\n' >foo
>>> three diffs showing added blank line with horizontal space <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@
hello world
+
goodbye world
$ hg ndiff -B
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@
hello world
+
goodbye world
$ hg ndiff -b
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@
hello world
+
goodbye world
>>> no diffs <<<
$ hg ndiff -Bb
Test added blank line with other whitespace:
$ printf 'hello world\n \t\ngoodbye world \n' >foo
>>> three diffs showing added blank line with other space <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@
-hello world
-goodbye world
+hello world
+
+goodbye world
$ hg ndiff -B
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@
-hello world
-goodbye world
+hello world
+
+goodbye world
$ hg ndiff -b
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,3 @@
hello world
+
goodbye world
>>> no diffs <<<
$ hg ndiff -Bb
Test whitespace changes:
$ printf 'helloworld\ngoodbye\tworld \n' >foo
>>> four diffs showing changed whitespace <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
-goodbye world
+helloworld
+goodbye world
$ hg ndiff -B
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
-goodbye world
+helloworld
+goodbye world
$ hg ndiff -b
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
+helloworld
goodbye world
$ hg ndiff -Bb
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,2 @@
-hello world
+helloworld
goodbye world
>>> no diffs <<<
$ hg ndiff -w
Test whitespace changes and blank lines:
$ printf 'helloworld\n\n\n\ngoodbye\tworld \n' >foo
>>> five diffs showing changed whitespace <<<
$ hg ndiff
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@
-hello world
-goodbye world
+helloworld
+
+
+
+goodbye world
$ hg ndiff -B
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@
-hello world
-goodbye world
+helloworld
+
+
+
+goodbye world
$ hg ndiff -b
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@
-hello world
+helloworld
+
+
+
goodbye world
$ hg ndiff -Bb
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@
-hello world
+helloworld
+
+
+
goodbye world
$ hg ndiff -w
diff -r 540c40a65b78 foo
--- a/foo
+++ b/foo
@@ -1,2 +1,5 @@
hello world
+
+
+
goodbye world
>>> no diffs <<<
$ hg ndiff -wB