Use consistent indentation, two spaces per level.
(scriptversion): New variable.
Change initializations like `variable=""' to `variable='.
(usage): New variable.
Use `test', not `['.
Use `test -n "$var"', not `[ x"$var" = x ]'.
Use `test -z "$var"', not `[ x"$var" != x ]'.
Alphabetize case entries.
Accept --help and --version options.
Remove unnecessary `else :' clauses.
Add a `Local variables' eval block to help emacs users update
the time-stamp variable added above.
Write diagnostics to stderr, not stdout.
Normalize spacing in diagnostics: use one space (not two, and not a TAB)
after the leading `install:'.
Add double quotes around `$src' here: $doit $instcmd "$src" "$dsttmp"
Paul Eggert