merge(3p/git): Merge git subtree at v2.29.2

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

third_party/git/compat/bswap.h

@@ -145,28 +145,6 @@ static inline uint64_t git_bswap64(uint64_t x)
 
 #endif
 
-/*
- * Performance might be improved if the CPU architecture is OK with
- * unaligned 32-bit loads and a fast ntohl() is available.
- * Otherwise fall back to byte loads and shifts which is portable,
- * and is faster on architectures with memory alignment issues.
- */
-
-#if !defined(NO_UNALIGNED_LOADS) && ( \
-    defined(__i386__) || defined(__x86_64__) || \
-    defined(_M_IX86) || defined(_M_X64) || \
-    defined(__ppc__) || defined(__ppc64__) || \
-    defined(__powerpc__) || defined(__powerpc64__) || \
-    defined(__s390__) || defined(__s390x__))
-
-#define get_be16(p)	ntohs(*(unsigned short *)(p))
-#define get_be32(p)	ntohl(*(unsigned int *)(p))
-#define get_be64(p)	ntohll(*(uint64_t *)(p))
-#define put_be32(p, v)	do { *(unsigned int *)(p) = htonl(v); } while (0)
-#define put_be64(p, v)	do { *(uint64_t *)(p) = htonll(v); } while (0)
-
-#else
-
 static inline uint16_t get_be16(const void *ptr)
 {
 	const unsigned char *p = ptr;
@@ -212,6 +190,4 @@ static inline void put_be64(void *ptr, uint64_t value)
 	p[7] = value >>  0;
 }
 
-#endif
-
 #endif /* COMPAT_BSWAP_H */