Merge branch 'pw/3.0-commentchar-auto-deprecation'

"core.commentChar=auto" that attempts to dynamically pick a
suitable comment character is non-workable, as it is too much
trouble to support for little benefit, and is marked as deprecated.

* pw/3.0-commentchar-auto-deprecation:
  commit: print advice when core.commentString=auto
  config: warn on core.commentString=auto
  breaking-changes: deprecate support for core.commentString=auto

1 files changed, 295 insertions, 2 deletions

diff --git a/config.c b/config.c
index e0ff35d426..74bf76a97e 100644
--- a/config.c
+++ b/config.c
@@ -8,9 +8,11 @@
 
 #include "git-compat-util.h"
 #include "abspath.h"
+#include "advice.h"
 #include "date.h"
 #include "branch.h"
 #include "config.h"
+#include "dir.h"
 #include "parse.h"
 #include "convert.h"
 #include "environment.h"
@@ -1948,10 +1950,290 @@ int git_configset_get_pathname(struct config_set *set, const char *key, char **d
 		return 1;
 }
 
+struct comment_char_config {
+	unsigned last_key_id;
+	bool auto_set;
+	bool auto_set_in_file;
+	struct strintmap key_flags;
+	size_t alloc, nr;
+	struct comment_char_config_item {
+		unsigned key_id;
+		char *path;
+		enum config_scope scope;
+	} *item;
+};
+
+#define COMMENT_CHAR_CFG_INIT {			\
+		.key_flags = STRINTMAP_INIT,	\
+	}
+
+static void comment_char_config_release(struct comment_char_config *config)
+{
+	strintmap_clear(&config->key_flags);
+	for (size_t i = 0; i < config->nr; i++)
+		free(config->item[i].path);
+	free(config->item);
+}
+
+/* Used to track whether the key occurs more than once in a given file */
+#define KEY_SEEN_ONCE 1u
+#define KEY_SEEN_TWICE 2u
+#define COMMENT_KEY_SHIFT(id) (2 * (id))
+#define COMMENT_KEY_MASK(id) (3u << COMMENT_KEY_SHIFT(id))
+
+static void set_comment_key_flags(struct comment_char_config *config,
+				  const char *path, unsigned id, unsigned value)
+{
+	unsigned old = strintmap_get(&config->key_flags, path);
+	unsigned new = (old & ~COMMENT_KEY_MASK(id)) |
+				value << COMMENT_KEY_SHIFT(id);
+
+	strintmap_set(&config->key_flags, path, new);
+}
+
+static unsigned get_comment_key_flags(struct comment_char_config *config,
+				      const char *path, unsigned id)
+{
+	unsigned value = strintmap_get(&config->key_flags, path);
+
+	return (value & COMMENT_KEY_MASK(id)) >> COMMENT_KEY_SHIFT(id);
+}
+
+static const char *comment_key_name(unsigned id)
+{
+	static const char *name[] = {
+		"core.commentChar",
+		"core.commentString",
+	};
+
+	if (id >= ARRAY_SIZE(name))
+		BUG("invalid comment key id");
+
+	return name[id];
+}
+
+static void comment_char_callback(const char *key, const char *value,
+				  const struct config_context *ctx, void *data)
+{
+	struct comment_char_config *config = data;
+	const struct key_value_info *kvi = ctx->kvi;
+	unsigned key_id;
+
+	if (!strcmp(key, "core.commentchar"))
+		key_id = 0;
+	else if (!strcmp(key, "core.commentstring"))
+		key_id = 1;
+	else
+		return;
+
+	config->last_key_id = key_id;
+	config->auto_set = value && !strcmp(value, "auto");
+	if (kvi->origin_type != CONFIG_ORIGIN_FILE) {
+		return;
+	} else if (get_comment_key_flags(config, kvi->filename, key_id)) {
+		set_comment_key_flags(config, kvi->filename, key_id,
+				      KEY_SEEN_TWICE);
+	} else {
+		struct comment_char_config_item *item;
+
+		ALLOC_GROW_BY(config->item, config->nr, 1, config->alloc);
+		item = &config->item[config->nr - 1];
+		item->key_id = key_id;
+		item->scope = kvi->scope;
+		item->path = xstrdup(kvi->filename);
+		set_comment_key_flags(config, kvi->filename, key_id,
+				      KEY_SEEN_ONCE);
+	}
+	config->auto_set_in_file = config->auto_set;
+}
+
+static void add_config_scope_arg(struct repository *repo, struct strbuf *buf,
+				 struct comment_char_config_item *item)
+{
+	char *global_config = git_global_config();
+	char *system_config = git_system_config();
+
+	if (item->scope == CONFIG_SCOPE_SYSTEM && access(item->path, W_OK)) {
+		/*
+		 * If the user cannot write to the system config recommend
+		 * setting the global config instead.
+		 */
+		strbuf_addstr(buf, "--global ");
+	} else if (fspatheq(item->path, system_config)) {
+		strbuf_addstr(buf, "--system ");
+	} else if (fspatheq(item->path, global_config)) {
+		strbuf_addstr(buf, "--global ");
+	} else if (fspatheq(item->path,
+			    mkpath("%s/config",
+				   repo_get_git_dir(repo)))) {
+		; /* --local is the default */
+	} else if (fspatheq(item->path,
+			    mkpath("%s/config.worktree",
+				   repo_get_common_dir(repo)))) {
+		strbuf_addstr(buf, "--worktree ");
+	} else {
+		const char *path = item->path;
+		const char *home = getenv("HOME");
+
+		strbuf_addstr(buf, "--file ");
+		if (home && !fspathncmp(path, home, strlen(home))) {
+			path += strlen(home);
+			if (!fspathncmp(path, "/", 1))
+				path++;
+			strbuf_addstr(buf, "~/");
+		}
+		sq_quote_buf_pretty(buf, path);
+		strbuf_addch(buf, ' ');
+	}
+
+	free(global_config);
+	free(system_config);
+}
+
+static bool can_unset_comment_char_config(struct comment_char_config *config)
+{
+	for (size_t i = 0; i < config->nr; i++) {
+		struct comment_char_config_item *item = &config->item[i];
+
+		if (item->scope == CONFIG_SCOPE_SYSTEM &&
+		    access(item->path, W_OK))
+			return false;
+	}
+
+	return true;
+}
+
+static void add_unset_auto_comment_char_advice(struct repository *repo,
+					       struct comment_char_config *config)
+{
+	struct strbuf buf = STRBUF_INIT;
+
+	if (!can_unset_comment_char_config(config))
+		return;
+
+	for (size_t i = 0; i < config->nr; i++) {
+		struct comment_char_config_item *item = &config->item[i];
+
+		strbuf_addstr(&buf, "    git config unset ");
+		add_config_scope_arg(repo, &buf, item);
+		if (get_comment_key_flags(config, item->path, item->key_id) == KEY_SEEN_TWICE)
+			strbuf_addstr(&buf, "--all ");
+		strbuf_addf(&buf, "%s\n", comment_key_name(item->key_id));
+	}
+	advise(_("\nTo use the default comment string (#) please run\n\n%s"),
+	       buf.buf);
+	strbuf_release(&buf);
+}
+
+static void add_comment_char_advice(struct repository *repo,
+				    struct comment_char_config *config)
+{
+	struct strbuf buf = STRBUF_INIT;
+	struct comment_char_config_item *item;
+	/* TRANSLATORS this is a place holder for the value of core.commentString */
+	const char *placeholder = _("<comment string>");
+
+	/*
+	 * If auto is set in the last file that we saw advise the user how to
+	 * update their config.
+	 */
+	if (!config->auto_set_in_file)
+		return;
+
+	add_unset_auto_comment_char_advice(repo, config);
+	item = &config->item[config->nr - 1];
+	strbuf_reset(&buf);
+	strbuf_addstr(&buf, "    git config set ");
+	add_config_scope_arg(repo, &buf, item);
+	strbuf_addf(&buf, "%s %s\n", comment_key_name(item->key_id),
+		    placeholder);
+	advise(_("\nTo set a custom comment string please run\n\n"
+		 "%s\nwhere '%s' is the string you wish to use.\n"),
+	       buf.buf, placeholder);
+	strbuf_release(&buf);
+}
+
+#undef KEY_SEEN_ONCE
+#undef KEY_SEEN_TWICE
+#undef COMMENT_KEY_SHIFT
+#undef COMMENT_KEY_MASK
+
+struct repo_config {
+	struct repository *repo;
+	struct comment_char_config comment_char_config;
+};
+
+#define REPO_CONFIG_INIT(repo_) {				\
+		.comment_char_config = COMMENT_CHAR_CFG_INIT,	\
+		.repo = repo_,					\
+	};
+
+static void repo_config_release(struct repo_config *config)
+{
+	comment_char_config_release(&config->comment_char_config);
+}
+
+#ifdef WITH_BREAKING_CHANGES
+static void check_auto_comment_char_config(struct repository *repo,
+					   struct comment_char_config *config)
+{
+	if (!config->auto_set)
+		return;
+
+	die_message(_("Support for '%s=auto' has been removed in Git 3.0"),
+		    comment_key_name(config->last_key_id));
+	add_comment_char_advice(repo, config);
+	die(NULL);
+}
+#else
+static void check_auto_comment_char_config(struct repository *repo,
+					   struct comment_char_config *config)
+{
+	extern bool warn_on_auto_comment_char;
+	const char *DEPRECATED_CONFIG_ENV =
+				"GIT_AUTO_COMMENT_CHAR_CONFIG_WARNING_GIVEN";
+
+	if (!config->auto_set || !warn_on_auto_comment_char)
+		return;
+
+	/*
+	 * Use an environment variable to ensure that subprocesses do not repeat
+	 * the warning.
+	 */
+	if (git_env_bool(DEPRECATED_CONFIG_ENV, false))
+		return;
+
+	setenv(DEPRECATED_CONFIG_ENV, "true", true);
+
+	warning(_("Support for '%s=auto' is deprecated and will be removed in "
+		  "Git 3.0"), comment_key_name(config->last_key_id));
+	add_comment_char_advice(repo, config);
+}
+#endif /* WITH_BREAKING_CHANGES */
+
+static void check_deprecated_config(struct repo_config *config)
+{
+	if (!config->repo->check_deprecated_config)
+			return;
+
+	check_auto_comment_char_config(config->repo,
+				       &config->comment_char_config);
+}
+
+static int repo_config_callback(const char *key, const char *value,
+				const struct config_context *ctx, void *data)
+{
+	struct repo_config *config = data;
+
+	comment_char_callback(key, value, ctx, &config->comment_char_config);
+	return config_set_callback(key, value, ctx, config->repo->config);
+}
+
 /* Functions use to read configuration from a repository */
 static void repo_read_config(struct repository *repo)
 {
 	struct config_options opts = { 0 };
+	struct repo_config config = REPO_CONFIG_INIT(repo);
 
 	opts.respect_includes = 1;
 	opts.commondir = repo->commondir;
@@ -1963,8 +2245,8 @@ static void repo_read_config(struct repository *repo)
 		git_configset_clear(repo->config);
 
 	git_configset_init(repo->config);
-	if (config_with_options(config_set_callback, repo->config, NULL,
-				repo, &opts) < 0)
+	if (config_with_options(repo_config_callback, &config, NULL, repo,
+				&opts) < 0)
 		/*
 		 * config_with_options() normally returns only
 		 * zero, as most errors are fatal, and
@@ -1977,6 +2259,8 @@ static void repo_read_config(struct repository *repo)
 		 * immediately.
 		 */
 		die(_("unknown error occurred while reading the configuration files"));
+	check_deprecated_config(&config);
+	repo_config_release(&config);
 }
 
 static void git_config_check_init(struct repository *repo)
@@ -2664,6 +2948,14 @@ int repo_config_set_multivar_in_file_gently(struct repository *r,
 	char *contents = NULL;
 	size_t contents_sz;
 	struct config_store_data store = CONFIG_STORE_INIT;
+	bool saved_check_deprecated_config = r->check_deprecated_config;
+
+	/*
+	 * Do not warn or die if there are deprecated config settings as
+	 * we want the user to be able to change those settings by running
+	 * "git config".
+	 */
+	r->check_deprecated_config = false;
 
 	validate_comment_string(comment);
 
@@ -2895,6 +3187,7 @@ out_free:
 	if (in_fd >= 0)
 		close(in_fd);
 	config_store_data_clear(&store);
+	r->check_deprecated_config = saved_check_deprecated_config;
 	return ret;
 
 write_err_out: