file called HEAD in your work tree, `git diff HEAD` is ambiguous, and
you have to say either `git diff HEAD --` or `git diff -- HEAD` to
disambiguate.
-
++
When writing a script that is expected to handle random user-input, it is
a good practice to make it explicit which arguments are which by placing
disambiguating `--` at appropriate places.
+ * Many commands allow wildcards in paths, but you need to protect
+ them from getting globbed by the shell. These two mean different
+ things:
++
+--------------------------------
+$ git checkout -- *.c
+$ git checkout -- \*.c
+--------------------------------
++
+The former lets your shell expand the fileglob, and you are asking
+the dot-C files in your working tree to be overwritten with the version
+in the index. The latter passes the `*.c` to Git, and you are asking
+the paths in the index that match the pattern to be checked out to your
+working tree. After running `git add hello.c; rm hello.c`, you will _not_
+see `hello.c` in your working tree with the former, but with the latter
+you will.
+
Here are the rules regarding the "flags" that you should follow when you are
scripting git:
`git log -1 HEAD` but write `git log -1 HEAD --`; the former will not work
if you happen to have a file called `HEAD` in the work tree.
+ * many commands allow a long option "--option" to be abbreviated
+ only to their unique prefix (e.g. if there is no other option
+ whose name begins with "opt", you may be able to spell "--opt" to
+ invoke the "--option" flag), but you should fully spell them out
+ when writing your scripts; later versions of Git may introduce a
+ new option whose name shares the same prefix, e.g. "--optimize",
+ to make a short prefix that used to be unique no longer unique.
+
ENHANCED OPTION PARSER
----------------------