Improve temporary dir creation

[aureliojargas]

Sometimes, the tests fail due to the temp dir creation routine:

#70 ./clitest --progress no test/ok-1.sh
--------------------------------------------------------------------------------
[FAILED #70, line 481] ./clitest --progress no test/ok-1.sh
@@ -1 +1,2 @@
-OK: 1 of 1 test passed
+mkdir: /var/folders/ns/p897hcp56wjgjt61yr7tbd980000gq/T//clitest.15322: File exists
+clitest: Error: cannot create temporary dir: /var/folders/ns/p897hcp56wjgjt61yr7tbd980000gq/T//clitest.15322
--------------------------------------------------------------------------------
#71 ./clitest -P dot test/ok-1.sh
#72 ./clitest -P no test/ok-1.sh
#73 ./clitest --progress . test/ok-1.sh
#74 ./clitest --progress . test/ok-2.sh

Is mktemp portable?

[vmmello]

my experience is that mktemp works well on several different systems. I've written scripts relying on mktemp that worked on CentOS/RH, Debian, Ubuntu and MacOS X without any change.

Or use mkdir and some portable randomizing function like:

head -c 1000 /dev/urandom | tr -dc A-Za-z0-9 | cut -b 1-15

[aureliojargas]

Unfortunately, mktemp is not portable: http://mywiki.wooledge.org/BashFAQ/062

Neither is /dev/random and /dev/urandom :(