init.sh: avoid Solaris 10 /bin/sh portability problem Solaris 10's /bin/sh does not pass '.' arguments 2..N to the sourced script: $ printf 'echo "$@"\n' > f; /bin/sh -c '. ./f bar' $ printf 'echo "$@"\n' > f; bash -c '. ./f bar' bar tests/init.sh relied on that, accepting a --set-path=DIR argument, and two tests used that idiom. * tests/init.sh: Update suggested usage comments. (path_prepend_): New function, to be used in place of the --src-path=DIR option. Disallow empty strings and strings containing ":". (setup_): Move PATH-prepending code into path_prepend_. * tests/test-pread.sh: Adapt to new usage. * tests/test-xalloc-die.sh: Likewise.