Update README.md with new manifest name, add cross-repo workflow

Change-Id: I75b2f48274dc580e096f0cd0e460e88615cca747

README.md

diff --git a/README.md b/README.md
index a735a83..143770d 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,7 @@
 curl -s https://raw.githubusercontent.com/vanadium/go.jiri/master/scripts/bootstrap_jiri | bash -s mojo
 export PATH=`pwd`/mojo/.jiri_root/scripts:`pwd`/mojo/depot_tools:$PATH
 cd mojo
-jiri import --name manifest mojo https://mojo.googlesource.com/mojo-manifest
+jiri import --name manifest mojo https://mojo.googlesource.com/manifest
 jiri update
 ```
 
@@ -39,11 +39,43 @@
 
 ```
 cd mojo/src
-# write some awesome stuff, commit to local branch
-git checkout -b branch_name
+
+# create a new change (makes a new local branch, checks it out)
+jiri cl new branch_name
+
+# write some awesome stuff, commit to branch_name
 vim some_file ...
 git commit ...
 
 # upload the patch to gerrit
 jiri cl mail
+
+# once the change is landed, clean up the branch
+jiri cl cleanup branch_name
 ```
+
+## Cross-repo changes
+
+Changes in two separate repos will be automatically tracked for you by `jiri`
+if you use the same branch name.
+
+```
+cd mojo/src
+jiri cl new add_feature_foo
+vim foo_related_files ...
+git commit ...
+
+cd mojo/src/base
+jiri cl new add_feature_foo
+vim more_foo_related_files ...
+git commit ...
+
+# upload both changes to gerrit
+jiri cl mail
+
+# cleanup the branch after the changes land
+jiri cl cleanup add_feature_foo
+```
+
+Multipart changes are tracked in gerrit via topics, are tested together, and
+can be landed in gerrit at the same time with `submit whole topic`.