Merge branch 'bc/sha-256-part-2'

SHA-256 migration work continues.

* bc/sha-256-part-2: (44 commits)
  remote-testgit: adapt for object-format
  bundle: detect hash algorithm when reading refs
  t5300: pass --object-format to git index-pack
  t5704: send object-format capability with SHA-256
  t5703: use object-format serve option
  t5702: offer an object-format capability in the test
  t/helper: initialize the repository for test-sha1-array
  remote-curl: avoid truncating refs with ls-remote
  t1050: pass algorithm to index-pack when outside repo
  builtin/index-pack: add option to specify hash algorithm
  remote-curl: detect algorithm for dumb HTTP by size
  builtin/ls-remote: initialize repository based on fetch
  t5500: make hash independent
  serve: advertise object-format capability for protocol v2
  connect: parse v2 refs with correct hash algorithm
  connect: pass full packet reader when parsing v2 refs
  Documentation/technical: document object-format for protocol v2
  t1302: expect repo format version 1 for SHA-256
  builtin/show-index: provide options to determine hash algo
  t5302: modernize test formatting
  ...

git-compat-util.h

@@ -868,6 +868,12 @@ char *xgetcwd(void);
 FILE *fopen_for_writing(const char *path);
 FILE *fopen_or_warn(const char *path, const char *mode);
 
+/*
+ * Like strncmp, but only return zero if s is NUL-terminated and exactly len
+ * characters long.  If it is not, consider it greater than t.
+ */
+int xstrncmpz(const char *s, const char *t, size_t len);
+
 /*
  * FREE_AND_NULL(ptr) is like free(ptr) followed by ptr = NULL. Note
  * that ptr is used twice, so don't pass e.g. ptr++.