[PATCH] autoconf: Use autoconf to check for libraries: openssl/crypto, curl, expat

[Jakub Narebski <jnareb@gmail.com>]

./configure script checks now if the following libraries are present:
 * -lcrypto (checks for SHA1_Init, sets NO_OPENSSL=YesPlease if not found)
 * -lcurl   (checks for curl_easy_setopt, sets NO_CURL=YesPlease if not found)
 * -lexpat  (checks for XML_ParserCreate, sets NO_EXPAT=YesPlease if not found)

Appropriate lines in config.mak are generated using MY_APPEND_LINE macro by adding
lines to temporary file config.mak.append

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---

Second patch in series introducing nonintrusive autoconf support to
git build process.

I'm not that sure about -lcrypto equals openssl.

 configure.ac |   17 ++++++++++++++++-
 1 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/configure.ac b/configure.ac
index 4003ff6..55d7a9b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -6,6 +6,21 @@ AC_INIT([git], [1.4.0], [git@vger.kernel
 
 AC_CONFIG_SRCDIR([git.c])
 
+# Definitions of macros
+# MY_APPEND_LINE(LINE)
+# --------------------
+# Append LINE to file config.mak.append
+AC_DEFUN([MY_APPEND_LINE],
+[[echo "$1" >> config.mak.append]])# AC_APPEND_LINE
+
+# Checks for libraries.
+AC_MSG_NOTICE(CHECKS for libraries)
+AC_CHECK_LIB([crypto], [SHA1_Init],,MY_APPEND_LINE(NO_OPENSSL=YesPlease))
+AC_CHECK_LIB([curl], [curl_easy_setopt],,MY_APPEND_LINE(NO_CURL=YesPlease))
+AC_CHECK_LIB([expat], [XML_ParserCreate],,MY_APPEND_LINE(NO_EXPAT=YesPlease))
+
 # Output files
-AC_CONFIG_FILES([config.mak])
+AC_CONFIG_FILES([config.mak:config.mak.in:config.mak.append], 
+[rm -f config.mak.append], 
+[echo >> config.mak.append])
 AC_OUTPUT
-- 
1.4.0