Remove dummy branch hack from tests

tests/test-diffdir

@@ -1,7 +1,6 b''
 #!/bin/sh
 
 hg init
-hg branch dummy # needed so -r "" doesn't point to the unnamed/default branch
 touch a
 hg add a
 hg ci -m "a" -d "1000000 0"

tests/test-diffdir.out

@@ -1,19 +1,19 b''
-diff -r 4da5fa99f904 b
+diff -r acd8075edac9 b
 --- /dev/null
 +++ b/b
 @@ -0,0 +1,1 @@
 +123
-diff -r 4da5fa99f904 b
+diff -r acd8075edac9 b
 --- /dev/null
 +++ b/b
 @@ -0,0 +1,1 @@
 +123
-diff -r 4da5fa99f904 a
+diff -r acd8075edac9 a
 --- a/a
 +++ b/a
 @@ -0,0 +1,1 @@
 +foo
-diff -r 4da5fa99f904 b
+diff -r acd8075edac9 b
 --- /dev/null
 +++ b/b
 @@ -0,0 +1,1 @@

tests/test-log

@@ -47,7 +47,6 b' hg log -pv d'
 # log --follow tests
 hg init ../follow
 cd ../follow
-hg branch dummy # needed so -r "" doesn't point to the unnamed/default branch
 echo base > base
 hg ci -Ambase -d '1 0'
 

tests/test-log.out

@@ -105,22 +105,19 b' adding base'
 1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 adding b1
 % log -f
-changeset:   3:07a62f044f0d
-branch:      dummy
+changeset:   3:e62f78d544b4
 tag:         tip
-parent:      1:fb3d4e35b279
+parent:      1:3d5bf5654eda
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b1
 
-changeset:   1:fb3d4e35b279
-branch:      dummy
+changeset:   1:3d5bf5654eda
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     r1
 
-changeset:   0:ea445bfed6b9
-branch:      dummy
+changeset:   0:67e992f2c4f3
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     base
@@ -128,21 +125,18 b' summary: base'
 1 files updated, 0 files merged, 1 files removed, 0 files unresolved
 adding b2
 % log -f -r 1:tip
-changeset:   1:fb3d4e35b279
-branch:      dummy
+changeset:   1:3d5bf5654eda
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     r1
 
-changeset:   2:e8882cbc828c
-branch:      dummy
+changeset:   2:60c670bf5b30
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     r2
 
-changeset:   3:07a62f044f0d
-branch:      dummy
-parent:      1:fb3d4e35b279
+changeset:   3:e62f78d544b4
+parent:      1:3d5bf5654eda
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b1
@@ -151,66 +145,57 b' 2 files updated, 0 files merged, 1 files'
 1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 (branch merge, don't forget to commit)
 % log --follow-first
-changeset:   6:0f621dafa603
-branch:      dummy
+changeset:   6:2404bbcab562
 tag:         tip
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b1.1
 
-changeset:   5:0cf53fb6dfd5
-branch:      dummy
-parent:      3:07a62f044f0d
-parent:      4:b76598590bc3
+changeset:   5:302e9dd6890d
+parent:      3:e62f78d544b4
+parent:      4:ddb82e70d1a1
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     m12
 
-changeset:   3:07a62f044f0d
-branch:      dummy
-parent:      1:fb3d4e35b279
+changeset:   3:e62f78d544b4
+parent:      1:3d5bf5654eda
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b1
 
-changeset:   1:fb3d4e35b279
-branch:      dummy
+changeset:   1:3d5bf5654eda
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     r1
 
-changeset:   0:ea445bfed6b9
-branch:      dummy
+changeset:   0:67e992f2c4f3
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     base
 
 % log -P 2
-changeset:   6:0f621dafa603
-branch:      dummy
+changeset:   6:2404bbcab562
 tag:         tip
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b1.1
 
-changeset:   5:0cf53fb6dfd5
-branch:      dummy
-parent:      3:07a62f044f0d
-parent:      4:b76598590bc3
+changeset:   5:302e9dd6890d
+parent:      3:e62f78d544b4
+parent:      4:ddb82e70d1a1
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     m12
 
-changeset:   4:b76598590bc3
-branch:      dummy
-parent:      0:ea445bfed6b9
+changeset:   4:ddb82e70d1a1
+parent:      0:67e992f2c4f3
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b2
 
-changeset:   3:07a62f044f0d
-branch:      dummy
-parent:      1:fb3d4e35b279
+changeset:   3:e62f78d544b4
+parent:      1:3d5bf5654eda
 user:        test
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b1