-e --> -f

[152334H]

A lot of Bad Things happen if someone accidentally ./adds a directory (instead of a normal file):

$ ./add .
sha1sum: /path/to/A/libc-database: Is a directory
Adding local libc /path/to/A/libc-database (id local-)
  -> Writing libc /path/to/A/libc-database to db/local-.so
cp: -r not specified; omitting directory '/path/to/A/libc-database'
  -> Writing symbols to db/local-.symbols
readelf: Error: '/path/to/A/libc-database' is not an ordinary file
objdump: Warning: '/path/to/A/libc-database' is not an ordinary file
objdump: Warning: '/path/to/A/libc-database' is not an ordinary file
  -> Writing version info

-f will check for a regular file, instead of an arbitrary file (-e)