[PATCH 3/3] Permit tests to be run as a (fake) root user

Skip tests that require sane behavior wrt permissions if the current uid is 0.

So now if you run

  fakeroot sh -c '
	make all test install install-doc prefix=/usr/local \
		DESTDIR=wherever >packaged-git.log 2>&1 &&
	cd wherever &&
	tar -cf - . |
	gzip
  ' >packaged-git.tar.gz

then this should successfully build a binary tarball for git, running some tests while at it.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
 Goals
 -----
 Before the POSIXPERM mechanism existed (which makes this change too
 easy to avoid considering), I think many people wanted to discourage
 running tests as root to avoid hosing people’s machines.  Which makes
 some sense.
 
 But it is possible and may even be valuable to run tests in a
 sandbox. [1] [8] If that were the only reason to run tests as root, I
 would suggest requiring some particular environment variable to be
 set as a safety.
 
 In Debian, I think it might be policy to allow building as “root”.  In
 this context, that almost always happens through some sort of ptrace or
 LD_PRELOAD hack like fakeroot.  If a user knows to, it is easy to fall
 back to building as an unprivileged user, but really I think a user
 should not have to know to. [2] [3]  If some non-POSIXPERM test fails
 when run as (fake) root, that is something that would be nice to
 know. [4]
 
 Which prerequisite?
 -------------------
 It is possible to use autoconf-style tests to check for each
 capability we would like to lack. [5]  Certainly, POSIXPERM does not
 actually describe the exact set of abilities one gains by running as
 an unprivileged user. [6]  But unsetting POSIXPERM does successfully
 convey a simple truth: if you run tests as root, you have lost the ability
 to pay attention to permissions and keep your sanity. [7]
 
 [1] http://thread.gmane.org/gmane.comp.version-control.git/86885/focus=87664
 [2] http://thread.gmane.org/gmane.comp.version-control.git/140128
 [3] http://thread.gmane.org/gmane.comp.version-control.git/17904/focus=17910
 [4] http://thread.gmane.org/gmane.comp.version-control.git/75561/focus=75568
 [5] http://thread.gmane.org/gmane.comp.version-control.git/18667
 [6] http://thread.gmane.org/gmane.comp.version-control.git/121502/focus=121531
 [7] http://thread.gmane.org/gmane.comp.version-control.git/116729/focus=118385
 [8] http://thread.gmane.org/gmane.comp.version-control.git/52654/focus=52689
     Holy cow, that Solaris bug is still not fixed [9].  Maybe it
     would be worthwhile to make an unlink() wrapper in compat/ to
     avoid new uses leaving users on such operating systems in danger.
 [9] http://bugs.opensolaris.org/view_bug.do?bug_id=6581318

Thanks for reading.  I hope the story was not too dull.

 t/test-lib.sh |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)