In addition to png.h, configure.ac and CMakeLists.txt, the script
ci_verify_version.sh is now able to verify libpng-config-head.in also.
For the benefit of readability, the old script ci_shellify.sh has been
split into smaller, independent scriptlets: libexec/ci_shellify_*.sh.
The linting script ci_lint.sh has been updated as needed.
Work around a limitation in the `shellcheck source` directive, which
does not recognize quotes in shellcheck versions older than 0.9.
Also extend the checks for YAML files over the entire source tree, in
preparation for the introduction of the GitHub Actions config file.
`PNG_LIBPNG_VER_BUILD` should be zero for public releases and non-zero
for development versions. The ci_verify_version.sh script should check
this requirement as such.
This program verifies the libpng source tree, expecting consistent
definitions of version numbers in the C source code, in the Autoconf
scripts, and in the CMake scripts.
The version verification is performed as follows. (Please note that
the version definitions in png.h are checked twice.)
* The files png.h, configure.ac and CMakeLists.txt are checked by
the ci_verify_version.sh program.
* The files png.h, png.c and pngtest.c are checked by the pngtest
program.