notes: implement helpers needed for note copying during rewrite

Implement helper functions to load the rewriting config, and to
actually copy the notes.  Also document the config.

Secondly, also implement an undocumented --for-rewrite=<cmd> option to
'git notes copy' which is used like --stdin, but also puts the
configuration for <cmd> into effect.  It will be needed to support the
copying in git-rebase.

Signed-off-by: Thomas Rast <[email protected]>
Acked-by: Johan Herland <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: trast

Documentation/config.txt

@@ -1305,6 +1305,36 @@ The effective value of "core.notesRef" (possibly overridden by
 GIT_NOTES_REF) is also implicitly added to the list of refs to be
 displayed.
 
+notes.rewrite.<command>::
+	When rewriting commits with <command> (currently `amend` or
+	`rebase`) and this variable is set to `true`, git
+	automatically copies your notes from the original to the
+	rewritten commit.  Defaults to `true`, but see
+	"notes.rewriteRef" below.
++
+This setting can be overridden with the `GIT_NOTES_REWRITE_REF`
+environment variable, which must be a colon separated list of refs or
+globs.
+
+notes.rewriteMode::
+	When copying notes during a rewrite (see the
+	"notes.rewrite.<command>" option), determines what to do if
+	the target commit already has a note.  Must be one of
+	`overwrite`, `concatenate`, or `ignore`.  Defaults to
+	`concatenate`.
++
+This setting can be overridden with the `GIT_NOTES_REWRITE_MODE`
+environment variable.
+
+notes.rewriteRef::
+	When copying notes during a rewrite, specifies the (fully
+	qualified) ref whose notes should be copied.  The ref may be a
+	glob, in which case notes in all matching refs will be copied.
+	You may also specify this configuration several times.
++
+Does not have a default value; you must configure this variable to
+enable note rewriting.
+
 pack.window::
 	The size of the window used by linkgit:git-pack-objects[1] when no
 	window size is given on the command line. Defaults to 10.

Documentation/git-notes.txt

@@ -35,6 +35,10 @@ This command always manipulates the notes specified in "core.notesRef"
 To change which notes are shown by 'git-log', see the
 "notes.displayRef" configuration.
 
+See the description of "notes.rewrite.<command>" in
+linkgit:git-config[1] for a way of carrying your notes across commands
+that rewrite commits.
+
 
 SUBCOMMANDS
 -----------

Documentation/githooks.txt

@@ -335,6 +335,10 @@ The 'extra-info' is again command-dependent.  If it is empty, the
 preceding SP is also omitted.  Currently, no commands pass any
 'extra-info'.
 
+The hook always runs after the automatic note copying (see
+"notes.rewrite.<command>" in linkgit:git-config.txt) has happened, and
+thus has access to these notes.
+
 The following command-specific comments apply:
 
 rebase::

builtin-notes.c

@@ -16,6 +16,7 @@
 #include "exec_cmd.h"
 #include "run-command.h"
 #include "parse-options.h"
+#include "string-list.h"
 
 static const char * const git_notes_usage[] = {
 	"git notes [list [<object>]]",
@@ -278,14 +279,121 @@ int commit_notes(struct notes_tree *t, const char *msg)
 	return 0;
 }
 
-int notes_copy_from_stdin(int force)
+
+combine_notes_fn *parse_combine_notes_fn(const char *v)
+{
+	if (!strcasecmp(v, "overwrite"))
+		return combine_notes_overwrite;
+	else if (!strcasecmp(v, "ignore"))
+		return combine_notes_ignore;
+	else if (!strcasecmp(v, "concatenate"))
+		return combine_notes_concatenate;
+	else
+		return NULL;
+}
+
+static int notes_rewrite_config(const char *k, const char *v, void *cb)
+{
+	struct notes_rewrite_cfg *c = cb;
+	if (!prefixcmp(k, "notes.rewrite.") && !strcmp(k+14, c->cmd)) {
+		c->enabled = git_config_bool(k, v);
+		return 0;
+	} else if (!c->mode_from_env && !strcmp(k, "notes.rewritemode")) {
+		if (!v)
+			config_error_nonbool(k);
+		c->combine = parse_combine_notes_fn(v);
+		if (!c->combine) {
+			error("Bad notes.rewriteMode value: '%s'", v);
+			return 1;
+		}
+		return 0;
+	} else if (!c->refs_from_env && !strcmp(k, "notes.rewriteref")) {
+		/* note that a refs/ prefix is implied in the
+		 * underlying for_each_glob_ref */
+		if (!prefixcmp(v, "refs/notes/"))
+			string_list_add_refs_by_glob(c->refs, v);
+		else
+			warning("Refusing to rewrite notes in %s"
+				" (outside of refs/notes/)", v);
+		return 0;
+	}
+
+	return 0;
+}
+
+
+struct notes_rewrite_cfg *init_copy_notes_for_rewrite(const char *cmd)
+{
+	struct notes_rewrite_cfg *c = xmalloc(sizeof(struct notes_rewrite_cfg));
+	const char *rewrite_mode_env = getenv(GIT_NOTES_REWRITE_MODE_ENVIRONMENT);
+	const char *rewrite_refs_env = getenv(GIT_NOTES_REWRITE_REF_ENVIRONMENT);
+	c->cmd = cmd;
+	c->enabled = 1;
+	c->combine = combine_notes_concatenate;
+	c->refs = xcalloc(1, sizeof(struct string_list));
+	c->refs->strdup_strings = 1;
+	c->refs_from_env = 0;
+	c->mode_from_env = 0;
+	if (rewrite_mode_env) {
+		c->mode_from_env = 1;
+		c->combine = parse_combine_notes_fn(rewrite_mode_env);
+		if (!c->combine)
+			error("Bad " GIT_NOTES_REWRITE_MODE_ENVIRONMENT
+			      " value: '%s'", rewrite_mode_env);
+	}
+	if (rewrite_refs_env) {
+		c->refs_from_env = 1;
+		string_list_add_refs_from_colon_sep(c->refs, rewrite_refs_env);
+	}
+	git_config(notes_rewrite_config, c);
+	if (!c->enabled || !c->refs->nr) {
+		string_list_clear(c->refs, 0);
+		free(c->refs);
+		free(c);
+		return NULL;
+	}
+	c->trees = load_notes_trees(c->refs);
+	string_list_clear(c->refs, 0);
+	free(c->refs);
+	return c;
+}
+
+int copy_note_for_rewrite(struct notes_rewrite_cfg *c,
+			  const unsigned char *from_obj, const unsigned char *to_obj)
+{
+	int ret = 0;
+	int i;
+	for (i = 0; c->trees[i]; i++)
+		ret = copy_note(c->trees[i], from_obj, to_obj, 1, c->combine) || ret;
+	return ret;
+}
+
+void finish_copy_notes_for_rewrite(struct notes_rewrite_cfg *c)
+{
+	int i;
+	for (i = 0; c->trees[i]; i++) {
+		commit_notes(c->trees[i], "Notes added by 'git notes copy'");
+		free_notes(c->trees[i]);
+	}
+	free(c->trees);
+	free(c);
+}
+
+int notes_copy_from_stdin(int force, const char *rewrite_cmd)
 {
 	struct strbuf buf = STRBUF_INIT;
+	struct notes_rewrite_cfg *c = NULL;
 	struct notes_tree *t;
 	int ret = 0;
 
-	init_notes(NULL, NULL, NULL, 0);
-	t = &default_notes_tree;
+	if (rewrite_cmd) {
+		c = init_copy_notes_for_rewrite(rewrite_cmd);
+		if (!c)
+			return 0;
+	} else {
+		init_notes(NULL, NULL, NULL, 0);
+		t = &default_notes_tree;
+	}
 
 	while (strbuf_getline(&buf, stdin, '\n') != EOF) {
 		unsigned char from_obj[20], to_obj[20];
@@ -302,7 +410,11 @@ int notes_copy_from_stdin(int force)
 		if (get_sha1(split[1]->buf, to_obj))
 			die("Failed to resolve '%s' as a valid ref.", split[1]->buf);
 
-		err = copy_note(t, from_obj, to_obj, force, combine_notes_overwrite);
+		if (rewrite_cmd)
+			err = copy_note_for_rewrite(c, from_obj, to_obj);
+		else
+			err = copy_note(t, from_obj, to_obj, force,
+					combine_notes_overwrite);
 
 		if (err) {
 			error("Failed to copy notes from '%s' to '%s'",
@@ -313,8 +425,12 @@ int notes_copy_from_stdin(int force)
 		strbuf_list_free(split);
 	}
 
-	commit_notes(t, "Notes added by 'git notes copy'");
-	free_notes(t);
+	if (!rewrite_cmd) {
+		commit_notes(t, "Notes added by 'git notes copy'");
+		free_notes(t);
+	} else {
+		finish_copy_notes_for_rewrite(c);
+	}
 	return ret;
 }
 
@@ -330,6 +446,7 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 	    remove = 0, prune = 0, force = 0, from_stdin = 0;
 	int given_object = 0, i = 1, retval = 0;
 	struct msg_arg msg = { 0, 0, STRBUF_INIT };
+	const char *rewrite_cmd = NULL;
 	struct option options[] = {
 		OPT_GROUP("Notes options"),
 		OPT_CALLBACK('m', "message", &msg, "MSG",
@@ -342,6 +459,8 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 			   "reuse specified note object", parse_reuse_arg),
 		OPT_BOOLEAN('f', "force", &force, "replace existing notes"),
 		OPT_BOOLEAN(0, "stdin", &from_stdin, "read objects from stdin"),
+		OPT_STRING(0, "for-rewrite", &rewrite_cmd, "command",
+			   "load rewriting config for <command> (implies --stdin)"),
 		OPT_END()
 	};
 
@@ -390,19 +509,23 @@ int cmd_notes(int argc, const char **argv, const char *prefix)
 		usage_with_options(git_notes_usage, options);
 	}
 
+	if (!copy && rewrite_cmd) {
+		error("cannot use --for-rewrite with %s subcommand.", argv[0]);
+		usage_with_options(git_notes_usage, options);
+	}
 	if (!copy && from_stdin) {
 		error("cannot use --stdin with %s subcommand.", argv[0]);
 		usage_with_options(git_notes_usage, options);
 	}
 
 	if (copy) {
 		const char *from_ref;
-		if (from_stdin) {
+		if (from_stdin || rewrite_cmd) {
 			if (argc > 1) {
 				error("too many parameters");
 				usage_with_options(git_notes_usage, options);
 			} else {
-				return notes_copy_from_stdin(force);
+				return notes_copy_from_stdin(force, rewrite_cmd);
 			}
 		}
 		if (argc < 3) {

builtin.h

@@ -20,6 +20,23 @@ extern int commit_tree(const char *msg, unsigned char *tree,
 		struct commit_list *parents, unsigned char *ret,
 		const char *author);
 extern int commit_notes(struct notes_tree *t, const char *msg);
+
+struct notes_rewrite_cfg {
+	struct notes_tree **trees;
+	const char *cmd;
+	int enabled;
+	combine_notes_fn *combine;
+	struct string_list *refs;
+	int refs_from_env;
+	int mode_from_env;
+};
+
+combine_notes_fn *parse_combine_notes_fn(const char *v);
+struct notes_rewrite_cfg *init_copy_notes_for_rewrite(const char *cmd);
+int copy_note_for_rewrite(struct notes_rewrite_cfg *c,
+			  const unsigned char *from_obj, const unsigned char *to_obj);
+void finish_copy_notes_for_rewrite(struct notes_rewrite_cfg *c);
+
 extern int check_pager_config(const char *cmd);
 
 extern int cmd_add(int argc, const char **argv, const char *prefix);

cache.h

@@ -386,6 +386,8 @@ static inline enum object_type object_type(unsigned int mode)
 #define GIT_NOTES_REF_ENVIRONMENT "GIT_NOTES_REF"
 #define GIT_NOTES_DEFAULT_REF "refs/notes/commits"
 #define GIT_NOTES_DISPLAY_REF_ENVIRONMENT "GIT_NOTES_DISPLAY_REF"
+#define GIT_NOTES_REWRITE_REF_ENVIRONMENT "GIT_NOTES_REWRITE_REF"
+#define GIT_NOTES_REWRITE_MODE_ENVIRONMENT "GIT_NOTES_REWRITE_MODE"
 
 extern int is_bare_repository_cfg;
 extern int is_bare_repository(void);