rebase: improve help text
- add a paragraph about default dest/source changesets
- option help: say "changeset" not "revision"
- option help: explain -b/--base better
- clarify that -a/--abort and -c/--continue are different from the
other options
% wide diffstat
a | 213 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 213 insertions(+), 0 deletions(-)
% diffstat width
a | 213 ++++++++++++++
1 files changed, 213 insertions(+), 0 deletions(-)
% narrow diffstat
a | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
% binary diffstat
b | 0
1 files changed, 0 insertions(+), 0 deletions(-)
% binary git diffstat
b | Bin
1 files changed, 0 insertions(+), 0 deletions(-)