Add checks for programs which are required for the test suite to run. All prerequisite programs are checked for existance, and if any are missing, a list of missing programs is printed, and the test suite is aborted. All programs currently used in the tests, except those in core-utils, are checked.

#!/bin/sh
hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "0 0"
ls
echo This is file b1 > b
hg add b
hg commit -m "commit #1" -d "0 0"
hg co 0
# B should disappear
ls