Add a local implementation of hstrerror for the system which do not have it

The function converts the value of h_errno (last error of name
resolver library, see netdb.h).
One of systems which supposedly do not have the function is SunOS.
POSIX does not mandate its presence.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -410,6 +410,7 @@ ifeq ($(uname_S),SunOS)
 	NEEDS_NSL = YesPlease
 	SHELL_PATH = /bin/bash
 	NO_STRCASESTR = YesPlease
+	NO_HSTRERROR = YesPlease
 	ifeq ($(uname_R),5.8)
 		NEEDS_LIBICONV = YesPlease
 		NO_UNSETENV = YesPlease
@@ -654,6 +655,10 @@ endif
 ifdef NO_PERL_MAKEMAKER
 	export NO_PERL_MAKEMAKER
 endif
+ifdef NO_HSTRERROR
+	COMPAT_CFLAGS += -DNO_HSTRERROR
+	COMPAT_OBJS += compat/hstrerror.o
+endif
 
 ifeq ($(TCLTK_PATH),)
 NO_TCLTK=NoThanks

compat/hstrerror.c

@@ -0,0 +1,21 @@
+#include <string.h>
+#include <stdio.h>
+#include <netdb.h>
+
+const char *githstrerror(int err)
+{
+	static char buffer[48];
+	switch (err)
+	{
+	case HOST_NOT_FOUND:
+		return "Authoritative answer: host not found";
+	case NO_DATA:
+		return "Valid name, no data record of requested type";
+	case NO_RECOVERY:
+		return "Non recoverable errors, FORMERR, REFUSED, NOTIMP";
+	case TRY_AGAIN:
+		return "Non-authoritative \"host not found\", or SERVERFAIL";
+	}
+	sprintf(buffer, "Name resolution error %d", err);
+	return buffer;
+}

git-compat-util.h

@@ -167,6 +167,11 @@ extern size_t gitstrlcpy(char *, const char *, size_t);
 extern uintmax_t gitstrtoumax(const char *, char **, int);
 #endif
 
+#ifdef NO_HSTRERROR
+#define hstrerror githstrerror
+extern const char *githstrerror(int herror);
+#endif
+
 extern void release_pack_memory(size_t, int);
 
 static inline char* xstrdup(const char *str)