Enforce exclusive output options

Currently, any output option (e.g., --version or --libs) will be set as
valid and what's output is at the mercy of the order of the output
handling code in main(). However, most combinations of output would make
no sense to be used together. For example, mixing --modversion and
--print-provides provides no way to differentiate between the output
from the options. Further, mixing --variable and --cflags currently
causes an error because there's no space separating the option outputs.

Instead, keep track of when an output option has been set and ignore
subsequent output options. There are currently two exceptions:

1. Any combination of --cflags* and --libs* are allowed.

2. Both --print-requires and --print-requires-private can be used
   together as the user may just not care which is private.

Freedesktop #54391 (https://bugs.freedesktop.org/show_bug.cgi?id=54391)

1 files changed, 15 insertions, 0 deletions

diff --git a/check/check-print-options b/check/check-print-options
index f9ce636..17aec1d 100755
--- a/check/check-print-options
+++ b/check/check-print-options
@@ -37,3 +37,18 @@ run_test --print-requires-private requires-test
 RESULT="sub1 Subdirectory package 1 - Test package 1 for subdirectory
 sub2 Subdirectory package 2 - Test package 2 for subdirectory"
 PKG_CONFIG_LIBDIR="$srcdir/sub" run_test --list-all
+
+# Check handling when multiple incompatible options are set
+RESULT="Ignoring incompatible output option \"--modversion\"
+$PACKAGE_VERSION"
+run_test --version --modversion simple
+
+RESULT="Ignoring incompatible output option \"--version\"
+1.0.0"
+run_test --modversion --version simple
+
+# --print-requires/--print-requires-private allowed together
+RESULT="public-dep >= 1
+private-dep >= 1"
+run_test --print-requires --print-requires-private requires-test
+run_test --print-requires-private --print-requires requires-test