Add library dependencies to the build

The libgit2 shared library must be linked with all the dynamic libraries
it depends (z, openssl).

These libraries are now automatically detected during the configuration
phase.

Also, removed the linking dependency on libgit2 which Scott added: if
you link libgit2 with itself, the universe could implode, and we don't
want that to happen.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

wscript

@@ -3,32 +3,46 @@ from waflib.Build import BuildContext, CleanContext, \
         InstallContext, UninstallContext
 
 CFLAGS = ["-g", "-O2", "-Wall", "-Wextra"]
+ALL_LIBS = ['z', 'crypto']
 
 def options(opt):
 	opt.load('compiler_c')
 	opt.add_option('--sha1', action='store', default='builtin',
 		help="Use the builtin SHA1 routines (builtin), the \
-PPC optimized version (ppc) or the SHA1 functions from OpenSSH (openssh)")
+PPC optimized version (ppc) or the SHA1 functions from OpenSSL (openssl)")
 
 def configure(conf):
+	# default configuration for C programs
 	conf.load('compiler_c')
 
-	if conf.options.sha1 not in ['openssh', 'ppc', 'builtin']:
+	# check for Z lib
+	conf.check(features='c cprogram', lib='z', uselib_store='z')
+
+	if conf.options.sha1 not in ['openssl', 'ppc', 'builtin']:
 		ctx.fatal('Invalid SHA1 option')
 
+	# check for libcrypto (openssl) if we are using its SHA1 functions
+	if conf.options.sha1 == 'openssl':
+		conf.check_cfg(package='libcrypto', args=['--cflags', '--libs'], uselib_store='crypto')
+
 	conf.env.sha1 = conf.options.sha1
 
 def build(bld):
 
+	# command '[build|clean|install|uninstall]-static'
 	if bld.variant == 'static':
 		build_library(bld, 'cstlib')
 
+	# command '[build|clean|install|uninstall]-shared'
 	elif bld.variant == 'shared':
 		build_library(bld, 'cshlib')
 
+	# command '[build|clean]-tests'
 	elif bld.variant == 'tests':
 		build_tests(bld)
 
+	# command 'build|clean|install|uninstall': by default, run
+	# the same command for both the static and the shared lib
 	else:
 		from waflib import Options
 		Options.commands = [bld.cmd + '-shared', bld.cmd + '-static'] + Options.commands
@@ -38,12 +52,22 @@ def build_library(bld, lib_str):
 
 	directory = bld.path
 
+	#------------------------------
+	# Default values
+	#------------------------------
+
 	sources = directory.ant_glob('src/*.c')
 	flags = CFLAGS
 	defines = []
 	visibility = True
 	os = 'unix'
 
+
+	#------------------------------
+	# OS-dependant configuration
+	#------------------------------
+
+	# Windows 32 (MSVC) platform configuration
 	if sys.platform == 'win32':
 		# windows configuration
 		flags = flags + ['-TC', '-W4', '-RTC1', '-Zi']
@@ -51,37 +75,61 @@ def build_library(bld, lib_str):
 		visibility = False
 		os = 'win32'
 
+	# Windows 32 Cygwin configuration
+	# (assume a POSIX-compilant system)
 	elif sys.platform == 'cygwin':
 		visibility = False
 
-	elif sys.platform == 'mingw': # TODO
+	# Windows 32 MinGW configuration (TODO)
+	elif sys.platform == 'mingw':
 		pass
 
-	if bld.env.sha1 == "openssh":
+	# Compile platform-dependant code
+	# E.g.	src/unix/*.c
+	#		src/win32/*.c
+	sources = sources + directory.ant_glob('src/%s/*.c' % os)
+
+	# Disable visibility on W32 platform
+	if not visibility:
+		flags.append('-fvisibility=hidden')
+
+
+	#------------------------------
+	# SHA1 Methods Source
+	#------------------------------
+
+	# OpenSSL library
+	if bld.env.sha1 == "openssl":
 		defines.append('OPENSSL_SHA1')
 
+	# builtin PPC methods
 	elif bld.env.sha1 == "ppc":
 		defines.append('PPC_SHA1')
 		sources.append('src/ppc/sha1.c')
 
+	# default builtins
 	else:
 		sources.append('src/block-sha1/sha1.c')
 
-	if not visibility:
-		flags.append('-fvisibility=hidden')
 
-	sources = sources + directory.ant_glob('src/%s/*.c' % os)
+	#------------------------------
+	# Build the main library
+	#------------------------------
 
+	# either as static or shared;
 	bld(features=['c', lib_str],
 		source=sources,
 		target='git2',
 		includes='src',
 		cflags=flags,
 		defines=defines,
-		stlib=['git2', 'z'],
 		install_path='${LIBDIR}',
+		use=ALL_LIBS	# link with all the libs we know (z, openssl);
+						# this is ignored for static builds
+						# and for libraries which have been disabled
 	)
 
+	# On Unix systems, build the Pkg-config entry file
 	if os == 'unix':
 		bld(rule="""sed -e 's#@prefix@#$(prefix)#' -e 's#@libdir@#$(libdir)#' < ${SRC} > ${TGT}""",
 			source='libgit2.pc.in',
@@ -89,8 +137,10 @@ def build_library(bld, lib_str):
 			install_path='${LIBDIR}/pkgconfig',
 		)
 
+	# Install headers
 	bld.install_files('${PREFIX}/include/git', directory.ant_glob('src/git/*.h'))
 
+
 def build_tests(bld):
 	import os
 
@@ -98,26 +148,33 @@ def build_tests(bld):
 		return
 
 	directory = bld.path
+
+	# Common object with the Test library methods
 	bld.objects(source=['tests/test_helpers.c', 'tests/test_lib.c'], includes=['src', 'tests'], target='test_helper')
 
+	# Build all tests in the tests/ folder
 	for test_file in directory.ant_glob('tests/t????-*.c'):
 		test_name, _ = os.path.splitext(os.path.basename(test_file.abspath()))
 
+		# Preprocess table of contents for each test
 		test_toc_file = directory.make_node('tests/%s.toc' % test_name)
-		if bld.cmd == 'clean-tests':
+		if bld.cmd == 'clean-tests': # cleanup; delete the generated TOC file
 			test_toc_file.delete()
-		elif bld.cmd == 'build-tests':
+		elif bld.cmd == 'build-tests': # build; create TOC
 			test_toc = bld.cmd_and_log(['grep', 'BEGIN_TEST', test_file.abspath()], quiet=True)
 			test_toc_file.write(test_toc)
 
+		# Build individual test (don't run)
 		bld.program(
 			source=[test_file, 'tests/test_main.c'],
 			target=test_name,
 			includes=['src', 'tests'],
 			defines=['TEST_TOC="%s.toc"' % test_name],
-			stlib=['git2', 'z'],
+			stlib=['git2'], # link with the git2 static lib we've just compiled'
 			stlibpath=directory.find_node('build/static/').abspath(),
-			use='test_helper')
+			use=['test_helper'] + ALL_LIBS  # link with all the libs we know
+											# libraries which are not enabled won't link
+		)
 
 
 class _test(BuildContext):