help: include unsafe SHA-1 build info in version

In 06c92da (Makefile: allow specifying a SHA-1 for non-cryptographic
uses, 2024-09-26), support for unsafe SHA-1 is added. Add the unsafe
SHA-1 build info to `git version --build-info` and update corresponding
documentation.

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

Author: jltobler

Documentation/git-version.adoc

@@ -22,6 +22,9 @@ OPTIONS
 --build-options::
 	Include additional information about how git was built for diagnostic
 	purposes.
++
+If built to use a faster SHA-1 implementation for non-cryptographic purposes,
+the implmentation used is denoted as "unsafe-SHA-1".
 
 GIT
 ---

help.c

@@ -784,6 +784,14 @@ static void get_sha_impl(struct strbuf *buf)
 	strbuf_addstr(buf, "SHA-1: Collision Detection\n");
 #endif
 
+#if defined(SHA1_OPENSSL_UNSAFE)
+	strbuf_addstr(buf, "unsafe-SHA-1: OpenSSL\n");
+#elif defined(SHA1_BLK_UNSAFE)
+	strbuf_addstr(buf, "unsafe-SHA-1: blk\n");
+#elif defined(SHA1_APPLE_UNSAFE)
+	strbuf_addstr(buf, "unsafe-SHA-1: Apple CommonCrypto\n");
+#endif
+
 #if defined(SHA256_OPENSSL)
 	strbuf_addstr(buf, "SHA-256: OpenSSL\n");
 #elif defined(SHA256_NETTLE)