- make the generic usage message more readable by splitting one long line into separate action options which can't (shouldn't) be used together
- make '-h' output to stdout instead of stderr
- use {} instead of [] for alternative options
- update man page accordingly.
New output:
```
# efibootmgr -h; echo $?
Usage:
efibootmgr [-v]
efibootmgr -c -l loader [-a] [-b bootnum] [-k kernel] [-L label]
efibootmgr -B -b bootnum
efibootmgr {-a|-A} -b bootnum
efibootmgr {-n|-N} -b bootnum
efibootmgr -o bootvarnum1,bootvarnum2,...
efibootmgr -t seconds
efibootmgr -T
0
# efibootmgr -w; echo $?
efibootmgr: invalid option -- w
Usage:
efibootmgr [-v]
efibootmgr -c -l loader [-a] [-b bootnum] [-k kernel] [-L label]
efibootmgr -B -b bootnum
efibootmgr {-a|-A} -b bootnum
efibootmgr {-n|-N} -b bootnum
efibootmgr -o bootvarnum1,bootvarnum2,...
efibootmgr -t seconds
efibootmgr -T
1
# efibootmgr -c; echo $?
Usage:
efibootmgr -c -l loader [-a] [-b bootnum] [-k kernel] [-L label]
1
```