tests/test-diff-change.out

extensions: load and configure extensions in well-defined phases

Extensions are now loaded with a call-graph like this:

  dispatch._dispatch
      extensions.loadall
          extensions.load
                # add foo module to extensions._extensions
          extensions.load
                # add bar module to extensions._extensions

          foo.uisetup(ui)
          bar.uisetup(ui)

      foo.extsetup()
      bar.extsetup()

      commands.table.update(foo.cmdtable)
      commands.table.update(bar.cmdtable)

  hg.repository
      foo.reposetup(ui, repo)
      bar.reposetup(ui, repo)

The uisetup calls could easily be moved out to dispatch._dispatch, but
have been kept in extensions.loadall since at least TortoiseHg calls
extensions.loadall and expects it to call uisetup.

The extensions.load function called uisetup. It now has an unused ui
argument which has been kept for backwards compatibility.

invoking hg diff --nodates --change 1:
diff -r 4bb65dda5db4 -r e9b286083166 file.txt
--- a/file.txt
+++ b/file.txt
@@ -1,1 +1,1 @@
-first
+second

invoking hg diff --nodates --change e9b286083166:
diff -r 4bb65dda5db4 -r e9b286083166 file.txt
--- a/file.txt
+++ b/file.txt
@@ -1,1 +1,1 @@
-first
+second

invoking hg diff --nodates --change 6:
diff -r e8a0797e73a6 -r aa9873050139 file.txt
--- a/file.txt
+++ b/file.txt
@@ -6,6 +6,6 @@
 5
 6
 7
-8
+y
 9
 10

EOF