tests: disallow the use of abbreviated options (by default)

Git's command-line parsers support uniquely abbreviated options, e.g.
`git init --ba` would automatically expand `--ba` to `--bare`.

This is a very convenient feature in every day life for Git users, in
particular when tab completion is not available.

However, it is not a good idea to rely on that in Git's test suite, as
something that is a unique abbreviation of a command line option today
might no longer be a unique abbreviation tomorrow.

For example, if a future contribution added a new mode
`git init --babyproofing` and a previously-introduced test case used the
fact that `git init --ba` expanded to `git init --bare`, that future
contribution would now have to touch seemingly unrelated tests just to
keep the test suite from failing.

So let's disallow abbreviated options in the test suite by default.

Note: for ease of implementation, this patch really only touches the
`parse-options` machinery: more and more hand-rolled option parsers are
converted to use that internal API, and more and more scripts are
converted to built-ins (naturally using the parse-options API, too), so
in practice this catches most issues, and is definitely the biggest bang
for the buck.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/t/README b/t/README
index 656288edce..9ed3051a1c 100644
--- a/t/README
+++ b/t/README
@@ -399,6 +399,10 @@ GIT_TEST_SIDEBAND_ALL=<boolean>, when true, overrides the
 fetch-pack to not request sideband-all (even if the server advertises
 sideband-all).
 
+GIT_TEST_DISALLOW_ABBREVIATED_OPTIONS=<boolean>, when true (which is
+the default when running tests), errors out when an abbreviated option
+is used.
+
 Naming Tests
 ------------