Makefile: make curl-config path configurable

There are situations, e.g. during cross compilation, where curl-config
program is not present in the PATH.

Make the makefile use a configurable curl-config program passed through
CURL_CONFIG variable which can be set through config.mak.

Also make this variable tunable through use of autoconf/configure. Configure
will set CURL_CONFIG variable in config.mak.autogen to whatever value has been
passed to ac_cv_prog_CURL_CONFIG.

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -39,6 +39,9 @@ all::
 # Define CURLDIR=/foo/bar if your curl header and library files are in
 # /foo/bar/include and /foo/bar/lib directories.
 #
+# Define CURL_CONFIG to curl's configuration program that prints information
+# about the library (e.g., its version number).  The default is 'curl-config'.
+#
 # Define NO_EXPAT if you do not have expat installed.  git-http-push is
 # not built, and you cannot push using http:// and https:// transports (dumb).
 #
@@ -425,6 +428,7 @@ TCL_PATH = tclsh
 TCLTK_PATH = wish
 XGETTEXT = xgettext
 MSGFMT = msgfmt
+CURL_CONFIG = curl-config
 PTHREAD_LIBS = -lpthread
 PTHREAD_CFLAGS =
 GCOV = gcov
@@ -1059,13 +1063,13 @@ else
 	REMOTE_CURL_NAMES = $(REMOTE_CURL_PRIMARY) $(REMOTE_CURL_ALIASES)
 	PROGRAM_OBJS += http-fetch.o
 	PROGRAMS += $(REMOTE_CURL_NAMES)
-	curl_check := $(shell (echo 070908; curl-config --vernum | sed -e '/^70[BC]/s/^/0/') 2>/dev/null | sort -r | sed -ne 2p)
+	curl_check := $(shell (echo 070908; $(CURL_CONFIG) --vernum | sed -e '/^70[BC]/s/^/0/') 2>/dev/null | sort -r | sed -ne 2p)
 	ifeq "$(curl_check)" "070908"
 		ifndef NO_EXPAT
 			PROGRAM_OBJS += http-push.o
 		endif
 	endif
-	curl_check := $(shell (echo 072200; curl-config --vernum | sed -e '/^70[BC]/s/^/0/') 2>/dev/null | sort -r | sed -ne 2p)
+	curl_check := $(shell (echo 072200; $(CURL_CONFIG) --vernum | sed -e '/^70[BC]/s/^/0/') 2>/dev/null | sort -r | sed -ne 2p)
 	ifeq "$(curl_check)" "072200"
 		USE_CURL_FOR_IMAP_SEND = YesPlease
 	endif

configure.ac

@@ -525,6 +525,19 @@ GIT_UNSTASH_FLAGS($CURLDIR)
 
 GIT_CONF_SUBST([NO_CURL])
 
+if test -z "$NO_CURL"; then
+
+AC_CHECK_PROG([CURL_CONFIG], [curl-config],
+[curl-config],
+[no])
+
+if test $CURL_CONFIG != no; then
+    GIT_CONF_SUBST([CURL_CONFIG])
+fi
+
+fi
+
+
 #
 # Define NO_EXPAT if you do not have expat installed.  git-http-push is
 # not built, and you cannot push using http:// and https:// transports.