These are all cases where we do a setup step of the form:

  for i in $foo; do
	  set_up $i || break
  done &&
  more_setup

would not notice a failure in set_up (because break always
returns a 0 exit code). These are just setup steps that we
do not expect to fail, but it does not hurt to be defensive.

Most can be fixed by converting the "break" to a "return 1"
(since we eval our tests inside a function for just this
purpose). A few of the loops are inside subshells, so we can
use just "exit 1" to break out of the subshell. And a few
can actually be made shorter by just unrolling the loop.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Many scripts compare actual and expected output using
"diff -u". This is nicer than "cmp" because the output shows
how the two differ. However, not all versions of diff
understand -u, leading to unnecessary test failure.

This adds a test_cmp function to the test scripts and
switches all "diff -u" invocations to use it. The function
uses the contents of "$GIT_TEST_CMP" to compare its
arguments; the default is "diff -u".

On systems with a less-capable diff, you can do:

  GIT_TEST_CMP=cmp make test

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

The earlier test stripped away expected number of 'z' but the output
would have been very hard to read once somebody broke the common tail
optimization.  Instead, count the number of 'z' and show it, to help
diagnosing the problem better in the future.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

We need to be extra careful recovering the removed common section, so
that we do not break context nor the changed incomplete line (i.e. the
last line that does not end with LF).

Signed-off-by: Junio C Hamano <gitster@pobox.com>