help: include SHA implementation in version info

When the `--build-options` flag is used with git-version(1), additional
information about the built version of Git is printed. During build
time, different SHA implementations may be configured, but this
information is not included in the version info.

Add the SHA implementations Git is built with to the version info.

Signed-off-by: Justin Tobler <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jltobler

help.c

@@ -768,6 +768,33 @@ char *help_unknown_cmd(const char *cmd)
 	exit(1);
 }
 
+static void get_sha_impl(struct strbuf *buf)
+{
+#if defined(SHA1_OPENSSL)
+	strbuf_addstr(buf, "SHA-1: OpenSSL\n");
+#elif defined(SHA1_BLK)
+	strbuf_addstr(buf, "SHA-1: blk\n");
+#elif defined(SHA1_APPLE)
+	strbuf_addstr(buf, "SHA-1: Apple CommonCrypto\n");
+#elif defined(DC_SHA1_EXTERNAL)
+	strbuf_addstr(buf, "SHA-1: Collision Detection (External)\n");
+#elif defined(DC_SHA1_SUBMODULE)
+	strbuf_addstr(buf, "SHA-1: Collision Detection (Submodule)\n");
+#elif defined(SHA1_DC)
+	strbuf_addstr(buf, "SHA-1: Collision Detection\n");
+#endif
+
+#if defined(SHA256_OPENSSL)
+	strbuf_addstr(buf, "SHA-256: OpenSSL\n");
+#elif defined(SHA256_NETTLE)
+	strbuf_addstr(buf, "SHA-256: Nettle\n");
+#elif defined(SHA256_GCRYPT)
+	strbuf_addstr(buf, "SHA-256: gcrypt\n");
+#elif defined(SHA256_BLK)
+	strbuf_addstr(buf, "SHA-256: blk\n");
+#endif
+}
+
 void get_version_info(struct strbuf *buf, int show_build_options)
 {
 	/*
@@ -803,6 +830,7 @@ void get_version_info(struct strbuf *buf, int show_build_options)
 #elif defined ZLIB_VERSION
 		strbuf_addf(buf, "zlib: %s\n", ZLIB_VERSION);
 #endif
+		get_sha_impl(buf);
 	}
 }