json: implement {shortlog} and {changelog} templates
These are the same dispatch function under the hood. The only difference
is the default number of entries to render and the template to use. So
it makes sense to use a shared template.
Format for {changelistentry} is similar to {changeset}. However, there
are differences to argument names and their values preventing us from
(easily) using the same template. (Perhaps there is room to consolidate
the templates as a follow-up.)
We're currently not recording some data in {changelistentry} that exists
in {changeset}. This includes the branch name. This should be added in
a follow-up. For now, something is better than nothing.
$ hg init
$ cat > a <<EOF
> a
> b
> c
> EOF
$ hg ci -Am adda
adding a
$ cat > a <<EOF
> d
> e
> f
> EOF
$ hg ci -m moda
$ hg diff --reverse -r0 -r1
diff -r 2855cdcfcbb7 -r 8e1805a3cf6e a
--- a/a Thu Jan 01 00:00:00 1970 +0000
+++ b/a Thu Jan 01 00:00:00 1970 +0000
@@ -1,3 +1,3 @@
-d
-e
-f
+a
+b
+c
$ cat >> a <<EOF
> g
> h
> EOF
$ hg diff --reverse --nodates
diff -r 2855cdcfcbb7 a
--- a/a
+++ b/a
@@ -1,5 +1,3 @@
d
e
f
-g
-h
should show removed file 'a' as being added
$ hg revert a
$ hg rm a
$ hg diff --reverse --nodates a
diff -r 2855cdcfcbb7 a
--- /dev/null
+++ b/a
@@ -0,0 +1,3 @@
+d
+e
+f
should show added file 'b' as being removed
$ echo b >> b
$ hg add b
$ hg diff --reverse --nodates b
diff -r 2855cdcfcbb7 b
--- a/b
+++ /dev/null
@@ -1,1 +0,0 @@
-b