test: improve docs for when using HEAD or similar flags

Closes #29791.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
add --devel to fetch docs
reword test docs
regenerate manual
doctor: Add check for install_name_tool

Closes #29593.
Update mpc to 0.26

This is a bugfix release.
mpc: add 0.26 bottle.