read-only mode

Here's a documentation stub. Please fix and finish it and place in some manual.

==Using git in read-only mode==
Let's say you just want to examine things. There is a fine line
between commands and options that just examine things vs. those that
change things. One might worry that they can't remember that fine line.

Therefore the safest way to ensure you are using git in 'read-only mode' is to
* su nobody, or
* chmod -R u-w . (and remember to chmod -R u+w when you are finished), or
* ???