git/attr.c

/*
 * Handle git attributes.  See gitattributes(5) for a description of
 * the file syntax, and attr.h for a description of the API.
 *
 * One basic design decision here is that we are not going to support
 * an insanely large number of attributes.
 */

#include "git-compat-util.h"
#include "config.h"
#include "environment.h"
#include "exec-cmd.h"
#include "attr.h"
#include "dir.h"
#include "gettext.h"
#include "path.h"
#include "utf8.h"
#include "quote.h"
#include "read-cache-ll.h"
#include "revision.h"
#include "object-store-ll.h"
#include "setup.h"
#include "thread-utils.h"
#include "tree-walk.h"
#include "object-name.h"

const char git_attr__true[] = "(builtin)true";
const char git_attr__false[] = "\0(builtin)false";
static const char git_attr__unknown[] = "(builtin)unknown";
#define ATTR__TRUE git_attr__true
#define ATTR__FALSE git_attr__false
#define ATTR__UNSET NULL
#define ATTR__UNKNOWN git_attr__unknown

struct git_attr {
	unsigned int attr_nr; /* unique attribute number */
	char name[FLEX_ARRAY]; /* attribute name */
};

const char *git_attr_name(const struct git_attr *attr)
{
	return attr->name;
}

struct attr_hashmap {
	struct hashmap map;
	pthread_mutex_t mutex;
};

static inline void hashmap_lock(struct attr_hashmap *map)
{
	pthread_mutex_lock(&map->mutex);
}

static inline void hashmap_unlock(struct attr_hashmap *map)
{
	pthread_mutex_unlock(&map->mutex);
}

/* The container for objects stored in "struct attr_hashmap" */
struct attr_hash_entry {
	struct hashmap_entry ent;
	const char *key; /* the key; memory should be owned by value */
	size_t keylen; /* length of the key */
	void *value; /* the stored value */
};

/* attr_hashmap comparison function */
static int attr_hash_entry_cmp(const void *cmp_data UNUSED,
			       const struct hashmap_entry *eptr,
			       const struct hashmap_entry *entry_or_key,
			       const void *keydata UNUSED)
{
	const struct attr_hash_entry *a, *b;

	a = container_of(eptr, const struct attr_hash_entry, ent);
	b = container_of(entry_or_key, const struct attr_hash_entry, ent);
	return (a->keylen != b->keylen) || strncmp(a->key, b->key, a->keylen);
}

/*
 * The global dictionary of all interned attributes.  This
 * is a singleton object which is shared between threads.
 * Access to this dictionary must be surrounded with a mutex.
 */
static struct attr_hashmap g_attr_hashmap = {
	.map = HASHMAP_INIT(attr_hash_entry_cmp, NULL),
};

/*
 * Retrieve the 'value' stored in a hashmap given the provided 'key'.
 * If there is no matching entry, return NULL.
 */
static void *attr_hashmap_get(struct attr_hashmap *map,
			      const char *key, size_t keylen)
{
	struct attr_hash_entry k;
	struct attr_hash_entry *e;

	hashmap_entry_init(&k.ent, memhash(key, keylen));
	k.key = key;
	k.keylen = keylen;
	e = hashmap_get_entry(&map->map, &k, ent, NULL);

	return e ? e->value : NULL;
}

/* Add 'value' to a hashmap based on the provided 'key'. */
static void attr_hashmap_add(struct attr_hashmap *map,
			     const char *key, size_t keylen,
			     void *value)
{
	struct attr_hash_entry *e;

	e = xmalloc(sizeof(struct attr_hash_entry));
	hashmap_entry_init(&e->ent, memhash(key, keylen));
	e->key = key;
	e->keylen = keylen;
	e->value = value;

	hashmap_add(&map->map, &e->ent);
}

struct all_attrs_item {
	const struct git_attr *attr;
	const char *value;
	/*
	 * If 'macro' is non-NULL, indicates that 'attr' is a macro based on
	 * the current attribute stack and contains a pointer to the match_attr
	 * definition of the macro
	 */
	const struct match_attr *macro;
};

/*
 * Reallocate and reinitialize the array of all attributes (which is used in
 * the attribute collection process) in 'check' based on the global dictionary
 * of attributes.
 */
static void all_attrs_init(struct attr_hashmap *map, struct attr_check *check)
{
	int i;
	unsigned int size;

	hashmap_lock(map);

	size = hashmap_get_size(&map->map);
	if (size < check->all_attrs_nr)
		BUG("interned attributes shouldn't be deleted");

	/*
	 * If the number of attributes in the global dictionary has increased
	 * (or this attr_check instance doesn't have an initialized all_attrs
	 * field), reallocate the provided attr_check instance's all_attrs
	 * field and fill each entry with its corresponding git_attr.
	 */
	if (size != check->all_attrs_nr) {
		struct attr_hash_entry *e;
		struct hashmap_iter iter;

		REALLOC_ARRAY(check->all_attrs, size);
		check->all_attrs_nr = size;

		hashmap_for_each_entry(&map->map, &iter, e,
					ent /* member name */) {
			const struct git_attr *a = e->value;
			check->all_attrs[a->attr_nr].attr = a;
		}
	}

	hashmap_unlock(map);

	/*
	 * Re-initialize every entry in check->all_attrs.
	 * This re-initialization can live outside of the locked region since
	 * the attribute dictionary is no longer being accessed.
	 */
	for (i = 0; i < check->all_attrs_nr; i++) {
		check->all_attrs[i].value = ATTR__UNKNOWN;
		check->all_attrs[i].macro = NULL;
	}
}

static int attr_name_valid(const char *name, size_t namelen)
{
	/*
	 * Attribute name cannot begin with '-' and must consist of
	 * characters from [-A-Za-z0-9_.].
	 */
	if (namelen <= 0 || *name == '-')
		return 0;
	while (namelen--) {
		char ch = *name++;
		if (! (ch == '-' || ch == '.' || ch == '_' ||
		       ('0' <= ch && ch <= '9') ||
		       ('a' <= ch && ch <= 'z') ||
		       ('A' <= ch && ch <= 'Z')) )
			return 0;
	}
	return 1;
}

static void report_invalid_attr(const char *name, size_t len,
				const char *src, int lineno)
{
	struct strbuf err = STRBUF_INIT;
	strbuf_addf(&err, _("%.*s is not a valid attribute name"),
		    (int) len, name);
	fprintf(stderr, "%s: %s:%d\n", err.buf, src, lineno);
	strbuf_release(&err);
}

/*
 * Given a 'name', lookup and return the corresponding attribute in the global
 * dictionary.  If no entry is found, create a new attribute and store it in
 * the dictionary.
 */
static const struct git_attr *git_attr_internal(const char *name, size_t namelen)
{
	struct git_attr *a;

	if (!attr_name_valid(name, namelen))
		return NULL;

	hashmap_lock(&g_attr_hashmap);

	a = attr_hashmap_get(&g_attr_hashmap, name, namelen);

	if (!a) {
		FLEX_ALLOC_MEM(a, name, name, namelen);
		a->attr_nr = hashmap_get_size(&g_attr_hashmap.map);

		attr_hashmap_add(&g_attr_hashmap, a->name, namelen, a);
		if (a->attr_nr != hashmap_get_size(&g_attr_hashmap.map) - 1)
			die(_("unable to add additional attribute"));
	}

	hashmap_unlock(&g_attr_hashmap);

	return a;
}

const struct git_attr *git_attr(const char *name)
{
	return git_attr_internal(name, strlen(name));
}

/* What does a matched pattern decide? */
struct attr_state {
	const struct git_attr *attr;
	const char *setto;
};

struct pattern {
	const char *pattern;
	int patternlen;
	int nowildcardlen;
	unsigned flags;		/* PATTERN_FLAG_* */
};

/*
 * One rule, as from a .gitattributes file.
 *
 * If is_macro is true, then u.attr is a pointer to the git_attr being
 * defined.
 *
 * If is_macro is false, then u.pat is the filename pattern to which the
 * rule applies.
 *
 * In either case, num_attr is the number of attributes affected by
 * this rule, and state is an array listing them.  The attributes are
 * listed as they appear in the file (macros unexpanded).
 */
struct match_attr {
	union {
		struct pattern pat;
		const struct git_attr *attr;
	} u;
	char is_macro;
	size_t num_attr;
	struct attr_state state[FLEX_ARRAY];
};

static const char blank[] = " \t\r\n";

/* Flags usable in read_attr() and parse_attr_line() family of functions. */
#define READ_ATTR_MACRO_OK (1<<0)
#define READ_ATTR_NOFOLLOW (1<<1)

/*
 * Parse a whitespace-delimited attribute state (i.e., "attr",
 * "-attr", "!attr", or "attr=value") from the string starting at src.
 * If e is not NULL, write the results to *e.  Return a pointer to the
 * remainder of the string (with leading whitespace removed), or NULL
 * if there was an error.
 */
static const char *parse_attr(const char *src, int lineno, const char *cp,
			      struct attr_state *e)
{
	const char *ep, *equals;
	size_t len;

	ep = cp + strcspn(cp, blank);
	equals = strchr(cp, '=');
	if (equals && ep < equals)
		equals = NULL;
	if (equals)
		len = equals - cp;
	else
		len = ep - cp;
	if (!e) {
		if (*cp == '-' || *cp == '!') {
			cp++;
			len--;
		}
		if (!attr_name_valid(cp, len)) {
			report_invalid_attr(cp, len, src, lineno);
			return NULL;
		}
	} else {
		/*
		 * As this function is always called twice, once with
		 * e == NULL in the first pass and then e != NULL in
		 * the second pass, no need for attr_name_valid()
		 * check here.
		 */
		if (*cp == '-' || *cp == '!') {
			e->setto = (*cp == '-') ? ATTR__FALSE : ATTR__UNSET;
			cp++;
			len--;
		}
		else if (!equals)
			e->setto = ATTR__TRUE;
		else {
			e->setto = xmemdupz(equals + 1, ep - equals - 1);
		}
		e->attr = git_attr_internal(cp, len);
	}
	return ep + strspn(ep, blank);
}

static struct match_attr *parse_attr_line(const char *line, const char *src,
					  int lineno, unsigned flags)
{
	size_t namelen, num_attr, i;
	const char *cp, *name, *states;
	struct match_attr *res = NULL;
	int is_macro;
	struct strbuf pattern = STRBUF_INIT;

	cp = line + strspn(line, blank);
	if (!*cp || *cp == '#')
		return NULL;
	name = cp;

	if (strlen(line) >= ATTR_MAX_LINE_LENGTH) {
		warning(_("ignoring overly long attributes line %d"), lineno);
		return NULL;
	}

	if (*cp == '"' && !unquote_c_style(&pattern, name, &states)) {
		name = pattern.buf;
		namelen = pattern.len;
	} else {
		namelen = strcspn(name, blank);
		states = name + namelen;
	}

	if (strlen(ATTRIBUTE_MACRO_PREFIX) < namelen &&
	    starts_with(name, ATTRIBUTE_MACRO_PREFIX)) {
		if (!(flags & READ_ATTR_MACRO_OK)) {
			fprintf_ln(stderr, _("%s not allowed: %s:%d"),
				   name, src, lineno);
			goto fail_return;
		}
		is_macro = 1;
		name += strlen(ATTRIBUTE_MACRO_PREFIX);
		name += strspn(name, blank);
		namelen = strcspn(name, blank);
		if (!attr_name_valid(name, namelen)) {
			report_invalid_attr(name, namelen, src, lineno);
			goto fail_return;
		}
	}
	else
		is_macro = 0;

	states += strspn(states, blank);

	/* First pass to count the attr_states */
	for (cp = states, num_attr = 0; *cp; num_attr++) {
		cp = parse_attr(src, lineno, cp, NULL);
		if (!cp)
			goto fail_return;
	}

	res = xcalloc(1, st_add3(sizeof(*res),
				 st_mult(sizeof(struct attr_state), num_attr),
				 is_macro ? 0 : namelen + 1));
	if (is_macro) {
		res->u.attr = git_attr_internal(name, namelen);
	} else {
		char *p = (char *)&(res->state[num_attr]);
		memcpy(p, name, namelen);
		res->u.pat.pattern = p;
		parse_path_pattern(&res->u.pat.pattern,
				      &res->u.pat.patternlen,
				      &res->u.pat.flags,
				      &res->u.pat.nowildcardlen);
		if (res->u.pat.flags & PATTERN_FLAG_NEGATIVE) {
			warning(_("Negative patterns are ignored in git attributes\n"
				  "Use '\\!' for literal leading exclamation."));
			goto fail_return;
		}
	}
	res->is_macro = is_macro;
	res->num_attr = num_attr;

	/* Second pass to fill the attr_states */
	for (cp = states, i = 0; *cp; i++) {
		cp = parse_attr(src, lineno, cp, &(res->state[i]));
	}

	strbuf_release(&pattern);
	return res;

fail_return:
	strbuf_release(&pattern);
	free(res);
	return NULL;
}

/*
 * Like info/exclude and .gitignore, the attribute information can
 * come from many places.
 *
 * (1) .gitattributes file of the same directory;
 * (2) .gitattributes file of the parent directory if (1) does not have
 *      any match; this goes recursively upwards, just like .gitignore.
 * (3) $GIT_DIR/info/attributes, which overrides both of the above.
 *
 * In the same file, later entries override the earlier match, so in the
 * global list, we would have entries from info/attributes the earliest
 * (reading the file from top to bottom), .gitattributes of the root
 * directory (again, reading the file from top to bottom) down to the
 * current directory, and then scan the list backwards to find the first match.
 * This is exactly the same as what is_excluded() does in dir.c to deal with
 * .gitignore file and info/excludes file as a fallback.
 */

struct attr_stack {
	struct attr_stack *prev;
	char *origin;
	size_t originlen;
	unsigned num_matches;
	unsigned alloc;
	struct match_attr **attrs;
};

static void attr_stack_free(struct attr_stack *e)
{
	unsigned i;