Merge branch 'jc/push-cas'

Allow a safer "rewind of the remote tip" push than blind "--force",
by requiring that the overwritten remote ref to be unchanged since
the new history to replace it was prepared.

The machinery is more or less ready.  The "--force" option is again
the big red button to override any safety, thanks to J6t's sanity
(the original round allowed --lockref to defeat --force).

The logic to choose the default implemented here is fragile
(e.g. "git fetch" after seeing a failure will update the
remote-tracking branch and will make the next "push" pass,
defeating the safety pretty easily).  It is suitable only for the
simplest workflows, and it may hurt users more than it helps them.

* jc/push-cas:
  push: teach --force-with-lease to smart-http transport
  send-pack: fix parsing of --force-with-lease option
  t5540/5541: smart-http does not support "--force-with-lease"
  t5533: test "push --force-with-lease"
  push --force-with-lease: tie it all together
  push --force-with-lease: implement logic to populate old_sha1_expect[]
  remote.c: add command line option parser for "--force-with-lease"
  builtin/push.c: use OPT_BOOL, not OPT_BOOLEAN
  cache.h: move remote/connect API out of it

1 files changed, 83 insertions, 0 deletions

diff --git a/remote.h b/remote.h
index 4db34980f6..131130a611 100644
--- a/remote.h
+++ b/remote.h
@@ -1,6 +1,8 @@
 #ifndef REMOTE_H
 #define REMOTE_H
 
+#include "parse-options.h"
+
 enum {
 	REMOTE_CONFIG,
 	REMOTE_REMOTES,
@@ -72,6 +74,56 @@ struct refspec {
 
 extern const struct refspec *tag_refspec;
 
+struct ref {
+	struct ref *next;
+	unsigned char old_sha1[20];
+	unsigned char new_sha1[20];
+	unsigned char old_sha1_expect[20]; /* used by expect-old */
+	char *symref;
+	unsigned int
+		force:1,
+		forced_update:1,
+		expect_old_sha1:1,
+		expect_old_no_trackback:1,
+		deletion:1,
+		matched:1;
+
+	/*
+	 * Order is important here, as we write to FETCH_HEAD
+	 * in numeric order. And the default NOT_FOR_MERGE
+	 * should be 0, so that xcalloc'd structures get it
+	 * by default.
+	 */
+	enum {
+		FETCH_HEAD_MERGE = -1,
+		FETCH_HEAD_NOT_FOR_MERGE = 0,
+		FETCH_HEAD_IGNORE = 1
+	} fetch_head_status;
+
+	enum {
+		REF_STATUS_NONE = 0,
+		REF_STATUS_OK,
+		REF_STATUS_REJECT_NONFASTFORWARD,
+		REF_STATUS_REJECT_ALREADY_EXISTS,
+		REF_STATUS_REJECT_NODELETE,
+		REF_STATUS_REJECT_FETCH_FIRST,
+		REF_STATUS_REJECT_NEEDS_FORCE,
+		REF_STATUS_REJECT_STALE,
+		REF_STATUS_UPTODATE,
+		REF_STATUS_REMOTE_REJECT,
+		REF_STATUS_EXPECTING_REPORT
+	} status;
+	char *remote_status;
+	struct ref *peer_ref; /* when renaming */
+	char name[FLEX_ARRAY]; /* more */
+};
+
+#define REF_NORMAL	(1u << 0)
+#define REF_HEADS	(1u << 1)
+#define REF_TAGS	(1u << 2)
+
+extern struct ref *find_ref_by_name(const struct ref *list, const char *name);
+
 struct ref *alloc_ref(const char *name);
 struct ref *copy_ref(const struct ref *ref);
 struct ref *copy_ref_list(const struct ref *ref);
@@ -85,6 +137,14 @@ int check_ref_type(const struct ref *ref, int flags);
  */
 void free_refs(struct ref *ref);
 
+struct extra_have_objects {
+	int nr, alloc;
+	unsigned char (*array)[20];
+};
+extern struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
+				     struct ref **list, unsigned int flags,
+				     struct extra_have_objects *);
+
 int resolve_remote_symref(struct ref *ref, struct ref *list);
 int ref_newer(const unsigned char *new_sha1, const unsigned char *old_sha1);
 
@@ -173,4 +233,27 @@ struct ref *guess_remote_head(const struct ref *head,
 /* Return refs which no longer exist on remote */
 struct ref *get_stale_heads(struct refspec *refs, int ref_count, struct ref *fetch_map);
 
+/*
+ * Compare-and-swap
+ */
+#define CAS_OPT_NAME "force-with-lease"
+
+struct push_cas_option {
+	unsigned use_tracking_for_rest:1;
+	struct push_cas {
+		unsigned char expect[20];
+		unsigned use_tracking:1;
+		char *refname;
+	} *entry;
+	int nr;
+	int alloc;
+};
+
+extern int parseopt_push_cas_option(const struct option *, const char *arg, int unset);
+extern int parse_push_cas_option(struct push_cas_option *, const char *arg, int unset);
+extern void clear_cas_option(struct push_cas_option *);
+
+extern int is_empty_cas(const struct push_cas_option *);
+void apply_push_cas(struct push_cas_option *, struct remote *, struct ref *);
+
 #endif