cache.h

#ifndef CACHE_H
#define CACHE_H

#include "git-compat-util.h"
#include "strbuf.h"
#include "hashmap.h"
#include "list.h"
#include "advice.h"
#include "gettext.h"
#include "convert.h"
#include "trace.h"
#include "string-list.h"
#include "pack-revindex.h"
#include "hash.h"
#include "path.h"
#include "sha1-array.h"
#include "repository.h"
#include "mem-pool.h"

#include <zlib.h>
typedef struct git_zstream {
	z_stream z;
	unsigned long avail_in;
	unsigned long avail_out;
	unsigned long total_in;
	unsigned long total_out;
	unsigned char *next_in;
	unsigned char *next_out;
} git_zstream;

void git_inflate_init(git_zstream *);
void git_inflate_init_gzip_only(git_zstream *);
void git_inflate_end(git_zstream *);
int git_inflate(git_zstream *, int flush);

void git_deflate_init(git_zstream *, int level);
void git_deflate_init_gzip(git_zstream *, int level);
void git_deflate_init_raw(git_zstream *, int level);
void git_deflate_end(git_zstream *);
int git_deflate_abort(git_zstream *);
int git_deflate_end_gently(git_zstream *);
int git_deflate(git_zstream *, int flush);
unsigned long git_deflate_bound(git_zstream *, unsigned long);

/* The length in bytes and in hex digits of an object name (SHA-1 value). */
#define GIT_SHA1_RAWSZ 20
#define GIT_SHA1_HEXSZ (2 * GIT_SHA1_RAWSZ)
/* The block size of SHA-1. */
#define GIT_SHA1_BLKSZ 64

/* The length in bytes and in hex digits of an object name (SHA-256 value). */
#define GIT_SHA256_RAWSZ 32
#define GIT_SHA256_HEXSZ (2 * GIT_SHA256_RAWSZ)
/* The block size of SHA-256. */
#define GIT_SHA256_BLKSZ 64

/* The length in byte and in hex digits of the largest possible hash value. */
#define GIT_MAX_RAWSZ GIT_SHA256_RAWSZ
#define GIT_MAX_HEXSZ GIT_SHA256_HEXSZ
/* The largest possible block size for any supported hash. */
#define GIT_MAX_BLKSZ GIT_SHA256_BLKSZ

struct object_id {
	unsigned char hash[GIT_MAX_RAWSZ];
};

#define the_hash_algo the_repository->hash_algo

#if defined(DT_UNKNOWN) && !defined(NO_D_TYPE_IN_DIRENT)
#define DTYPE(de)	((de)->d_type)
#else
#undef DT_UNKNOWN
#undef DT_DIR
#undef DT_REG
#undef DT_LNK
#define DT_UNKNOWN	0
#define DT_DIR		1
#define DT_REG		2
#define DT_LNK		3
#define DTYPE(de)	DT_UNKNOWN
#endif

/* unknown mode (impossible combination S_IFIFO|S_IFCHR) */
#define S_IFINVALID     0030000

/*
 * A "directory link" is a link to another git directory.
 *
 * The value 0160000 is not normally a valid mode, and
 * also just happens to be S_IFDIR + S_IFLNK
 */
#define S_IFGITLINK	0160000
#define S_ISGITLINK(m)	(((m) & S_IFMT) == S_IFGITLINK)

/*
 * Some mode bits are also used internally for computations.
 *
 * They *must* not overlap with any valid modes, and they *must* not be emitted
 * to outside world - i.e. appear on disk or network. In other words, it's just
 * temporary fields, which we internally use, but they have to stay in-house.
 *
 * ( such approach is valid, as standard S_IF* fits into 16 bits, and in Git
 *   codebase mode is `unsigned int` which is assumed to be at least 32 bits )
 */

/* used internally in tree-diff */
#define S_DIFFTREE_IFXMIN_NEQ	0x80000000


/*
 * Intensive research over the course of many years has shown that
 * port 9418 is totally unused by anything else. Or
 *
 *	Your search - "port 9418" - did not match any documents.
 *
 * as www.google.com puts it.
 *
 * This port has been properly assigned for git use by IANA:
 * git (Assigned-9418) [I06-050728-0001].
 *
 *	git  9418/tcp   git pack transfer service
 *	git  9418/udp   git pack transfer service
 *
 * with Linus Torvalds <torvalds@osdl.org> as the point of
 * contact. September 2005.
 *
 * See http://www.iana.org/assignments/port-numbers
 */
#define DEFAULT_GIT_PORT 9418

/*
 * Basic data structures for the directory cache
 */

#define CACHE_SIGNATURE 0x44495243	/* "DIRC" */
struct cache_header {
	uint32_t hdr_signature;
	uint32_t hdr_version;
	uint32_t hdr_entries;
};

#define INDEX_FORMAT_LB 2
#define INDEX_FORMAT_UB 4

/*
 * The "cache_time" is just the low 32 bits of the
 * time. It doesn't matter if it overflows - we only
 * check it for equality in the 32 bits we save.
 */
struct cache_time {
	uint32_t sec;
	uint32_t nsec;
};

struct stat_data {
	struct cache_time sd_ctime;
	struct cache_time sd_mtime;
	unsigned int sd_dev;
	unsigned int sd_ino;
	unsigned int sd_uid;
	unsigned int sd_gid;
	unsigned int sd_size;
};

struct cache_entry {
	struct hashmap_entry ent;
	struct stat_data ce_stat_data;
	unsigned int ce_mode;
	unsigned int ce_flags;
	unsigned int mem_pool_allocated;
	unsigned int ce_namelen;
	unsigned int index;	/* for link extension */
	struct object_id oid;
	char name[FLEX_ARRAY]; /* more */
};

#define CE_STAGEMASK (0x3000)
#define CE_EXTENDED  (0x4000)
#define CE_VALID     (0x8000)
#define CE_STAGESHIFT 12

/*
 * Range 0xFFFF0FFF in ce_flags is divided into
 * two parts: in-memory flags and on-disk ones.
 * Flags in CE_EXTENDED_FLAGS will get saved on-disk
 * if you want to save a new flag, add it in
 * CE_EXTENDED_FLAGS
 *
 * In-memory only flags
 */
#define CE_UPDATE            (1 << 16)
#define CE_REMOVE            (1 << 17)
#define CE_UPTODATE          (1 << 18)
#define CE_ADDED             (1 << 19)

#define CE_HASHED            (1 << 20)
#define CE_FSMONITOR_VALID   (1 << 21)
#define CE_WT_REMOVE         (1 << 22) /* remove in work directory */
#define CE_CONFLICTED        (1 << 23)

#define CE_UNPACKED          (1 << 24)
#define CE_NEW_SKIP_WORKTREE (1 << 25)

/* used to temporarily mark paths matched by pathspecs */
#define CE_MATCHED           (1 << 26)

#define CE_UPDATE_IN_BASE    (1 << 27)
#define CE_STRIP_NAME        (1 << 28)

/*
 * Extended on-disk flags
 */
#define CE_INTENT_TO_ADD     (1 << 29)
#define CE_SKIP_WORKTREE     (1 << 30)
/* CE_EXTENDED2 is for future extension */
#define CE_EXTENDED2         (1U << 31)

#define CE_EXTENDED_FLAGS (CE_INTENT_TO_ADD | CE_SKIP_WORKTREE)

/*
 * Safeguard to avoid saving wrong flags:
 *  - CE_EXTENDED2 won't get saved until its semantic is known
 *  - Bits in 0x0000FFFF have been saved in ce_flags already
 *  - Bits in 0x003F0000 are currently in-memory flags
 */
#if CE_EXTENDED_FLAGS & 0x803FFFFF
#error "CE_EXTENDED_FLAGS out of range"
#endif

/* Forward structure decls */
struct pathspec;
struct child_process;
struct tree;

/*
 * Copy the sha1 and stat state of a cache entry from one to
 * another. But we never change the name, or the hash state!
 */
static inline void copy_cache_entry(struct cache_entry *dst,
				    const struct cache_entry *src)
{
	unsigned int state = dst->ce_flags & CE_HASHED;
	int mem_pool_allocated = dst->mem_pool_allocated;

	/* Don't copy hash chain and name */
	memcpy(&dst->ce_stat_data, &src->ce_stat_data,
			offsetof(struct cache_entry, name) -
			offsetof(struct cache_entry, ce_stat_data));

	/* Restore the hash state */
	dst->ce_flags = (dst->ce_flags & ~CE_HASHED) | state;

	/* Restore the mem_pool_allocated flag */
	dst->mem_pool_allocated = mem_pool_allocated;
}

static inline unsigned create_ce_flags(unsigned stage)
{
	return (stage << CE_STAGESHIFT);
}

#define ce_namelen(ce) ((ce)->ce_namelen)
#define ce_size(ce) cache_entry_size(ce_namelen(ce))
#define ce_stage(ce) ((CE_STAGEMASK & (ce)->ce_flags) >> CE_STAGESHIFT)
#define ce_uptodate(ce) ((ce)->ce_flags & CE_UPTODATE)
#define ce_skip_worktree(ce) ((ce)->ce_flags & CE_SKIP_WORKTREE)
#define ce_mark_uptodate(ce) ((ce)->ce_flags |= CE_UPTODATE)
#define ce_intent_to_add(ce) ((ce)->ce_flags & CE_INTENT_TO_ADD)

#define ce_permissions(mode) (((mode) & 0100) ? 0755 : 0644)
static inline unsigned int create_ce_mode(unsigned int mode)
{
	if (S_ISLNK(mode))
		return S_IFLNK;
	if (S_ISDIR(mode) || S_ISGITLINK(mode))
		return S_IFGITLINK;
	return S_IFREG | ce_permissions(mode);
}
static inline unsigned int ce_mode_from_stat(const struct cache_entry *ce,
					     unsigned int mode)
{
	extern int trust_executable_bit, has_symlinks;
	if (!has_symlinks && S_ISREG(mode) &&
	    ce && S_ISLNK(ce->ce_mode))
		return ce->ce_mode;
	if (!trust_executable_bit && S_ISREG(mode)) {
		if (ce && S_ISREG(ce->ce_mode))
			return ce->ce_mode;
		return create_ce_mode(0666);
	}
	return create_ce_mode(mode);
}
static inline int ce_to_dtype(const struct cache_entry *ce)
{
	unsigned ce_mode = ntohl(ce->ce_mode);
	if (S_ISREG(ce_mode))
		return DT_REG;
	else if (S_ISDIR(ce_mode) || S_ISGITLINK(ce_mode))
		return DT_DIR;
	else if (S_ISLNK(ce_mode))
		return DT_LNK;
	else
		return DT_UNKNOWN;
}
static inline unsigned int canon_mode(unsigned int mode)
{
	if (S_ISREG(mode))
		return S_IFREG | ce_permissions(mode);
	if (S_ISLNK(mode))
		return S_IFLNK;
	if (S_ISDIR(mode))
		return S_IFDIR;
	return S_IFGITLINK;
}

#define cache_entry_size(len) (offsetof(struct cache_entry,name) + (len) + 1)

#define SOMETHING_CHANGED	(1 << 0) /* unclassified changes go here */
#define CE_ENTRY_CHANGED	(1 << 1)
#define CE_ENTRY_REMOVED	(1 << 2)
#define CE_ENTRY_ADDED		(1 << 3)
#define RESOLVE_UNDO_CHANGED	(1 << 4)
#define CACHE_TREE_CHANGED	(1 << 5)
#define SPLIT_INDEX_ORDERED	(1 << 6)
#define UNTRACKED_CHANGED	(1 << 7)
#define FSMONITOR_CHANGED	(1 << 8)

struct split_index;
struct untracked_cache;

struct index_state {
	struct cache_entry **cache;
	unsigned int version;
	unsigned int cache_nr, cache_alloc, cache_changed;
	struct string_list *resolve_undo;
	struct cache_tree *cache_tree;
	struct split_index *split_index;
	struct cache_time timestamp;
	unsigned name_hash_initialized : 1,
		 initialized : 1,
		 drop_cache_tree : 1;
	struct hashmap name_hash;
	struct hashmap dir_hash;
	struct object_id oid;
	struct untracked_cache *untracked;
	uint64_t fsmonitor_last_update;
	struct ewah_bitmap *fsmonitor_dirty;
	struct mem_pool *ce_mem_pool;
};

extern struct index_state the_index;

/* Name hashing */
extern int test_lazy_init_name_hash(struct index_state *istate, int try_threaded);
extern void add_name_hash(struct index_state *istate, struct cache_entry *ce);
extern void remove_name_hash(struct index_state *istate, struct cache_entry *ce);
extern void free_name_hash(struct index_state *istate);


/* Cache entry creation and cleanup */

/*
 * Create cache_entry intended for use in the specified index. Caller
 * is responsible for discarding the cache_entry with
 * `discard_cache_entry`.
 */
struct cache_entry *make_cache_entry(struct index_state *istate,
				     unsigned int mode,
				     const struct object_id *oid,
				     const char *path,
				     int stage,
				     unsigned int refresh_options);

struct cache_entry *make_empty_cache_entry(struct index_state *istate,
					   size_t name_len);

/*
 * Create a cache_entry that is not intended to be added to an index.
 * Caller is responsible for discarding the cache_entry
 * with `discard_cache_entry`.
 */
struct cache_entry *make_transient_cache_entry(unsigned int mode,
					       const struct object_id *oid,
					       const char *path,
					       int stage);

struct cache_entry *make_empty_transient_cache_entry(size_t name_len);

/*
 * Discard cache entry.
 */
void discard_cache_entry(struct cache_entry *ce);

/*
 * Check configuration if we should perform extra validation on cache
 * entries.
 */
int should_validate_cache_entries(void);

/*
 * Duplicate a cache_entry. Allocate memory for the new entry from a
 * memory_pool. Takes into account cache_entry fields that are meant
 * for managing the underlying memory allocation of the cache_entry.
 */
struct cache_entry *dup_cache_entry(const struct cache_entry *ce, struct index_state *istate);

/*
 * Validate the cache entries in the index.  This is an internal
 * consistency check that the cache_entry structs are allocated from
 * the expected memory pool.
 */
void validate_cache_entries(const struct index_state *istate);

#ifndef NO_THE_INDEX_COMPATIBILITY_MACROS
#define active_cache (the_index.cache)
#define active_nr (the_index.cache_nr)
#define active_alloc (the_index.cache_alloc)
#define active_cache_changed (the_index.cache_changed)
#define active_cache_tree (the_index.cache_tree)

#define read_cache() read_index(&the_index)
#define read_cache_from(path) read_index_from(&the_index, (path), (get_git_dir()))
#define read_cache_preload(pathspec) read_index_preload(&the_index, (pathspec), 0)
#define is_cache_unborn() is_index_unborn(&the_index)
#define read_cache_unmerged() read_index_unmerged(&the_index)
#define discard_cache() discard_index(&the_index)
#define unmerged_cache() unmerged_index(&the_index)
#define cache_name_pos(name, namelen) index_name_pos(&the_index,(name),(namelen))
#define add_cache_entry(ce, option) add_index_entry(&the_index, (ce), (option))
#define rename_cache_entry_at(pos, new_name) rename_index_entry_at(&the_index, (pos), (new_name))
#define remove_cache_entry_at(pos) remove_index_entry_at(&the_index, (pos))
#define remove_file_from_cache(path) remove_file_from_index(&the_index, (path))
#define add_to_cache(path, st, flags) add_to_index(&the_index, (path), (st), (flags))
#define add_file_to_cache(path, flags) add_file_to_index(&the_index, (path), (flags))
#define chmod_cache_entry(ce, flip) chmod_index_entry(&the_index, (ce), (flip))
#define refresh_cache(flags) refresh_index(&the_index, (flags), NULL, NULL, NULL)
#define ce_match_stat(ce, st, options) ie_match_stat(&the_index, (ce), (st), (options))
#define ce_modified(ce, st, options) ie_modified(&the_index, (ce), (st), (options))
#define cache_dir_exists(name, namelen) index_dir_exists(&the_index, (name), (namelen))
#define cache_file_exists(name, namelen, igncase) index_file_exists(&the_index, (name), (namelen), (igncase))
#define cache_name_is_other(name, namelen) index_name_is_other(&the_index, (name), (namelen))
#define resolve_undo_clear() resolve_undo_clear_index(&the_index)
#define unmerge_cache_entry_at(at) unmerge_index_entry_at(&the_index, at)
#define unmerge_cache(pathspec) unmerge_index(&the_index, pathspec)
#define read_blob_data_from_cache(path, sz) read_blob_data_from_index(&the_index, (path), (sz))
#endif

#define TYPE_BITS 3

/*
 * Values in this enum (except those outside the 3 bit range) are part
 * of pack file format. See Documentation/technical/pack-format.txt
 * for more information.
 */
enum object_type {
	OBJ_BAD = -1,
	OBJ_NONE = 0,
	OBJ_COMMIT = 1,
	OBJ_TREE = 2,
	OBJ_BLOB = 3,
	OBJ_TAG = 4,
	/* 5 for future expansion */
	OBJ_OFS_DELTA = 6,
	OBJ_REF_DELTA = 7,
	OBJ_ANY,
	OBJ_MAX
};

static inline enum object_type object_type(unsigned int mode)
{
	return S_ISDIR(mode) ? OBJ_TREE :
		S_ISGITLINK(mode) ? OBJ_COMMIT :
		OBJ_BLOB;
}

/* Double-check local_repo_env below if you add to this list. */
#define GIT_DIR_ENVIRONMENT "GIT_DIR"
#define GIT_COMMON_DIR_ENVIRONMENT "GIT_COMMON_DIR"
#define GIT_NAMESPACE_ENVIRONMENT "GIT_NAMESPACE"
#define GIT_WORK_TREE_ENVIRONMENT "GIT_WORK_TREE"
#define GIT_PREFIX_ENVIRONMENT "GIT_PREFIX"
#define GIT_SUPER_PREFIX_ENVIRONMENT "GIT_INTERNAL_SUPER_PREFIX"
#define DEFAULT_GIT_DIR_ENVIRONMENT ".git"
#define DB_ENVIRONMENT "GIT_OBJECT_DIRECTORY"
#define INDEX_ENVIRONMENT "GIT_INDEX_FILE"
#define GRAFT_ENVIRONMENT "GIT_GRAFT_FILE"
#define GIT_SHALLOW_FILE_ENVIRONMENT "GIT_SHALLOW_FILE"
#define TEMPLATE_DIR_ENVIRONMENT "GIT_TEMPLATE_DIR"
#define CONFIG_ENVIRONMENT "GIT_CONFIG"
#define CONFIG_DATA_ENVIRONMENT "GIT_CONFIG_PARAMETERS"
#define EXEC_PATH_ENVIRONMENT "GIT_EXEC_PATH"
#define CEILING_DIRECTORIES_ENVIRONMENT "GIT_CEILING_DIRECTORIES"
#define NO_REPLACE_OBJECTS_ENVIRONMENT "GIT_NO_REPLACE_OBJECTS"
#define GIT_REPLACE_REF_BASE_ENVIRONMENT "GIT_REPLACE_REF_BASE"
#define GITATTRIBUTES_FILE ".gitattributes"
#define INFOATTRIBUTES_FILE "info/attributes"
#define ATTRIBUTE_MACRO_PREFIX "[attr]"
#define GITMODULES_FILE ".gitmodules"
#define GITMODULES_INDEX ":.gitmodules"
#define GITMODULES_HEAD "HEAD:.gitmodules"
#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"
#define GIT_LITERAL_PATHSPECS_ENVIRONMENT "GIT_LITERAL_PATHSPECS"
#define GIT_GLOB_PATHSPECS_ENVIRONMENT "GIT_GLOB_PATHSPECS"
#define GIT_NOGLOB_PATHSPECS_ENVIRONMENT "GIT_NOGLOB_PATHSPECS"
#define GIT_ICASE_PATHSPECS_ENVIRONMENT "GIT_ICASE_PATHSPECS"
#define GIT_QUARANTINE_ENVIRONMENT "GIT_QUARANTINE_PATH"
#define GIT_OPTIONAL_LOCKS_ENVIRONMENT "GIT_OPTIONAL_LOCKS"
#define GIT_TEXT_DOMAIN_DIR_ENVIRONMENT "GIT_TEXTDOMAINDIR"

/*
 * Environment variable used in handshaking the wire protocol.
 * Contains a colon ':' separated list of keys with optional values
 * 'key[=value]'.  Presence of unknown keys and values must be
 * ignored.
 */
#define GIT_PROTOCOL_ENVIRONMENT "GIT_PROTOCOL"
/* HTTP header used to handshake the wire protocol */
#define GIT_PROTOCOL_HEADER "Git-Protocol"

/*
 * This environment variable is expected to contain a boolean indicating
 * whether we should or should not treat:
 *
 *   GIT_DIR=foo.git git ...
 *
 * as if GIT_WORK_TREE=. was given. It's not expected that users will make use
 * of this, but we use it internally to communicate to sub-processes that we
 * are in a bare repo. If not set, defaults to true.
 */
#define GIT_IMPLICIT_WORK_TREE_ENVIRONMENT "GIT_IMPLICIT_WORK_TREE"

/*
 * Repository-local GIT_* environment variables; these will be cleared
 * when git spawns a sub-process that runs inside another repository.
 * The array is NULL-terminated, which makes it easy to pass in the "env"
 * parameter of a run-command invocation, or to do a simple walk.
 */
extern const char * const local_repo_env[];

extern void setup_git_env(const char *git_dir);

/*
 * Returns true iff we have a configured git repository (either via
 * setup_git_directory, or in the environment via $GIT_DIR).
 */
int have_git_dir(void);

extern int is_bare_repository_cfg;
extern int is_bare_repository(void);
extern int is_inside_git_dir(void);
extern char *git_work_tree_cfg;
extern int is_inside_work_tree(void);
extern const char *get_git_dir(void);
extern const char *get_git_common_dir(void);
extern char *get_object_directory(void);
extern char *get_index_file(void);
extern char *get_graft_file(struct repository *r);
extern void set_git_dir(const char *path);
extern int get_common_dir_noenv(struct strbuf *sb, const char *gitdir);
extern int get_common_dir(struct strbuf *sb, const char *gitdir);
extern const char *get_git_namespace(void);
extern const char *strip_namespace(const char *namespaced_ref);
extern const char *get_super_prefix(void);
extern const char *get_git_work_tree(void);

/*
 * Return true if the given path is a git directory; note that this _just_
 * looks at the directory itself. If you want to know whether "foo/.git"
 * is a repository, you must feed that path, not just "foo".
 */
extern int is_git_directory(const char *path);

/*
 * Return 1 if the given path is the root of a git repository or
 * submodule, else 0. Will not return 1 for bare repositories with the
 * exception of creating a bare repository in "foo/.git" and calling
 * is_git_repository("foo").
 *
 * If we run into read errors, we err on the side of saying "yes, it is",
 * as we usually consider sub-repos precious, and would prefer to err on the
 * side of not disrupting or deleting them.
 */
extern int is_nonbare_repository_dir(struct strbuf *path);

#define READ_GITFILE_ERR_STAT_FAILED 1
#define READ_GITFILE_ERR_NOT_A_FILE 2
#define READ_GITFILE_ERR_OPEN_FAILED 3
#define READ_GITFILE_ERR_READ_FAILED 4
#define READ_GITFILE_ERR_INVALID_FORMAT 5
#define READ_GITFILE_ERR_NO_PATH 6
#define READ_GITFILE_ERR_NOT_A_REPO 7
#define READ_GITFILE_ERR_TOO_LARGE 8
extern void read_gitfile_error_die(int error_code, const char *path, const char *dir);
extern const char *read_gitfile_gently(const char *path, int *return_error_code);
#define read_gitfile(path) read_gitfile_gently((path), NULL)
extern const char *resolve_gitdir_gently(const char *suspect, int *return_error_code);
#define resolve_gitdir(path) resolve_gitdir_gently((path), NULL)

extern void set_git_work_tree(const char *tree);

#define ALTERNATE_DB_ENVIRONMENT "GIT_ALTERNATE_OBJECT_DIRECTORIES"

extern void setup_work_tree(void);
/*
 * Find the commondir and gitdir of the repository that contains the current
 * working directory, without changing the working directory or other global
 * state. The result is appended to commondir and gitdir.  If the discovered
 * gitdir does not correspond to a worktree, then 'commondir' and 'gitdir' will
 * both have the same result appended to the buffer.  The return value is
 * either 0 upon success and non-zero if no repository was found.
 */
extern int discover_git_directory(struct strbuf *commondir,
				  struct strbuf *gitdir);
extern const char *setup_git_directory_gently(int *);
extern const char *setup_git_directory(void);
extern char *prefix_path(const char *prefix, int len, const char *path);
extern char *prefix_path_gently(const char *prefix, int len, int *remaining, const char *path);

/*
 * Concatenate "prefix" (if len is non-zero) and "path", with no
 * connecting characters (so "prefix" should end with a "/").
 * Unlike prefix_path, this should be used if the named file does
 * not have to interact with index entry; i.e. name of a random file
 * on the filesystem.
 *
 * The return value is always a newly allocated string (even if the
 * prefix was empty).
 */
extern char *prefix_filename(const char *prefix, const char *path);

extern int check_filename(const char *prefix, const char *name);
extern void verify_filename(const char *prefix,
			    const char *name,
			    int diagnose_misspelt_rev);
extern void verify_non_filename(const char *prefix, const char *name);
extern int path_inside_repo(const char *prefix, const char *path);

#define INIT_DB_QUIET 0x0001
#define INIT_DB_EXIST_OK 0x0002

extern int init_db(const char *git_dir, const char *real_git_dir,
		   const char *template_dir, unsigned int flags);

extern void sanitize_stdfds(void);
extern int daemonize(void);

#define alloc_nr(x) (((x)+16)*3/2)

/*
 * Realloc the buffer pointed at by variable 'x' so that it can hold
 * at least 'nr' entries; the number of entries currently allocated
 * is 'alloc', using the standard growing factor alloc_nr() macro.
 *
 * DO NOT USE any expression with side-effect for 'x', 'nr', or 'alloc'.
 */
#define ALLOC_GROW(x, nr, alloc) \
	do { \
		if ((nr) > alloc) { \
			if (alloc_nr(alloc) < (nr)) \
				alloc = (nr); \
			else \
				alloc = alloc_nr(alloc); \
			REALLOC_ARRAY(x, alloc); \
		} \
	} while (0)

/* Initialize and use the cache information */
struct lock_file;
extern int read_index(struct index_state *);
extern void preload_index(struct index_state *index,
			  const struct pathspec *pathspec,
			  unsigned int refresh_flags);
extern int read_index_preload(struct index_state *,
			      const struct pathspec *pathspec,
			      unsigned int refresh_flags);
extern int do_read_index(struct index_state *istate, const char *path,
			 int must_exist); /* for testting only! */
extern int read_index_from(struct index_state *, const char *path,
			   const char *gitdir);
extern int is_index_unborn(struct index_state *);
extern int read_index_unmerged(struct index_state *);

/* For use with `write_locked_index()`. */
#define COMMIT_LOCK		(1 << 0)
#define SKIP_IF_UNCHANGED	(1 << 1)

/*
 * Write the index while holding an already-taken lock. Close the lock,
 * and if `COMMIT_LOCK` is given, commit it.
 *
 * Unless a split index is in use, write the index into the lockfile.
 *
 * With a split index, write the shared index to a temporary file,
 * adjust its permissions and rename it into place, then write the
 * split index to the lockfile. If the temporary file for the shared
 * index cannot be created, fall back to the behavior described in
 * the previous paragraph.
 *
 * With `COMMIT_LOCK`, the lock is always committed or rolled back.
 * Without it, the lock is closed, but neither committed nor rolled
 * back.
 *
 * If `SKIP_IF_UNCHANGED` is given and the index is unchanged, nothing
 * is written (and the lock is rolled back if `COMMIT_LOCK` is given).
 */
extern int write_locked_index(struct index_state *, struct lock_file *lock, unsigned flags);

extern int discard_index(struct index_state *);
extern void move_index_extensions(struct index_state *dst, struct index_state *src);
extern int unmerged_index(const struct index_state *);

/**
 * Returns 1 if istate differs from tree, 0 otherwise.  If tree is NULL,
 * compares istate to HEAD.  If tree is NULL and on an unborn branch,
 * returns 1 if there are entries in istate, 0 otherwise.  If an strbuf is
 * provided, the space-separated list of files that differ will be appended
 * to it.
 */
extern int index_has_changes(struct index_state *istate,
			     struct tree *tree,
			     struct strbuf *sb);

extern int verify_path(const char *path, unsigned mode);
extern int strcmp_offset(const char *s1, const char *s2, size_t *first_change);
extern int index_dir_exists(struct index_state *istate, const char *name, int namelen);
extern void adjust_dirname_case(struct index_state *istate, char *name);
extern struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int igncase);

/*
 * Searches for an entry defined by name and namelen in the given index.
 * If the return value is positive (including 0) it is the position of an
 * exact match. If the return value is negative, the negated value minus 1
 * is the position where the entry would be inserted.
 * Example: The current index consists of these files and its stages:
 *
 *   b#0, d#0, f#1, f#3
 *
 * index_name_pos(&index, "a", 1) -> -1
 * index_name_pos(&index, "b", 1) ->  0
 * index_name_pos(&index, "c", 1) -> -2
 * index_name_pos(&index, "d", 1) ->  1
 * index_name_pos(&index, "e", 1) -> -3
 * index_name_pos(&index, "f", 1) -> -3
 * index_name_pos(&index, "g", 1) -> -5
 */
extern int index_name_pos(const struct index_state *, const char *name, int namelen);

#define ADD_CACHE_OK_TO_ADD 1		/* Ok to add */
#define ADD_CACHE_OK_TO_REPLACE 2	/* Ok to replace file/directory */
#define ADD_CACHE_SKIP_DFCHECK 4	/* Ok to skip DF conflict checks */
#define ADD_CACHE_JUST_APPEND 8		/* Append only; tree.c::read_tree() */
#define ADD_CACHE_NEW_ONLY 16		/* Do not replace existing ones */
#define ADD_CACHE_KEEP_CACHE_TREE 32	/* Do not invalidate cache-tree */
#define ADD_CACHE_RENORMALIZE 64        /* Pass along HASH_RENORMALIZE */
extern int add_index_entry(struct index_state *, struct cache_entry *ce, int option);
extern void rename_index_entry_at(struct index_state *, int pos, const char *new_name);

/* Remove entry, return true if there are more entries to go. */
extern int remove_index_entry_at(struct index_state *, int pos);

extern void remove_marked_cache_entries(struct index_state *istate, int invalidate);
extern int remove_file_from_index(struct index_state *, const char *path);
#define ADD_CACHE_VERBOSE 1
#define ADD_CACHE_PRETEND 2
#define ADD_CACHE_IGNORE_ERRORS	4
#define ADD_CACHE_IGNORE_REMOVAL 8
#define ADD_CACHE_INTENT 16
/*
 * These two are used to add the contents of the file at path
 * to the index, marking the working tree up-to-date by storing
 * the cached stat info in the resulting cache entry.  A caller
 * that has already run lstat(2) on the path can call
 * add_to_index(), and all others can call add_file_to_index();
 * the latter will do necessary lstat(2) internally before
 * calling the former.
 */
extern int add_to_index(struct index_state *, const char *path, struct stat *, int flags);
extern int add_file_to_index(struct index_state *, const char *path, int flags);

extern int chmod_index_entry(struct index_state *, struct cache_entry *ce, char flip);
extern int ce_same_name(const struct cache_entry *a, const struct cache_entry *b);
extern void set_object_name_for_intent_to_add_entry(struct cache_entry *ce);
extern int index_name_is_other(const struct index_state *, const char *, int);
extern void *read_blob_data_from_index(const struct index_state *, const char *, unsigned long *);

/* do stat comparison even if CE_VALID is true */
#define CE_MATCH_IGNORE_VALID		01
/* do not check the contents but report dirty on racily-clean entries */
#define CE_MATCH_RACY_IS_DIRTY		02
/* do stat comparison even if CE_SKIP_WORKTREE is true */
#define CE_MATCH_IGNORE_SKIP_WORKTREE	04
/* ignore non-existent files during stat update  */
#define CE_MATCH_IGNORE_MISSING		0x08
/* enable stat refresh */
#define CE_MATCH_REFRESH		0x10
/* don't refresh_fsmonitor state or do stat comparison even if CE_FSMONITOR_VALID is true */
#define CE_MATCH_IGNORE_FSMONITOR 0X20
extern int is_racy_timestamp(const struct index_state *istate,
			     const struct cache_entry *ce);
extern int ie_match_stat(struct index_state *, const struct cache_entry *, struct stat *, unsigned int);
extern int ie_modified(struct index_state *, const struct cache_entry *, struct stat *, unsigned int);

#define HASH_WRITE_OBJECT 1
#define HASH_FORMAT_CHECK 2
#define HASH_RENORMALIZE  4
extern int index_fd(struct index_state *istate, struct object_id *oid, int fd, struct stat *st, enum object_type type, const char *path, unsigned flags);
extern int index_path(struct index_state *istate, struct object_id *oid, const char *path, struct stat *st, unsigned flags);

/*
 * Record to sd the data from st that we use to check whether a file
 * might have changed.
 */
extern void fill_stat_data(struct stat_data *sd, struct stat *st);

/*
 * Return 0 if st is consistent with a file not having been changed
 * since sd was filled.  If there are differences, return a
 * combination of MTIME_CHANGED, CTIME_CHANGED, OWNER_CHANGED,
 * INODE_CHANGED, and DATA_CHANGED.
 */
extern int match_stat_data(const struct stat_data *sd, struct stat *st);
extern int match_stat_data_racy(const struct index_state *istate,
				const struct stat_data *sd, struct stat *st);

extern void fill_stat_cache_info(struct cache_entry *ce, struct stat *st);

#define REFRESH_REALLY		0x0001	/* ignore_valid */
#define REFRESH_UNMERGED	0x0002	/* allow unmerged */
#define REFRESH_QUIET		0x0004	/* be quiet about it */
#define REFRESH_IGNORE_MISSING	0x0008	/* ignore non-existent */
#define REFRESH_IGNORE_SUBMODULES	0x0010	/* ignore submodules */
#define REFRESH_IN_PORCELAIN	0x0020	/* user friendly output, not "needs update" */
#define REFRESH_PROGRESS	0x0040  /* show progress bar if stderr is tty */
extern int refresh_index(struct index_state *, unsigned int flags, const struct pathspec *pathspec, char *seen, const char *header_msg);
extern struct cache_entry *refresh_cache_entry(struct index_state *, struct cache_entry *, unsigned int);

/*
 * Opportunistically update the index but do not complain if we can't.
 * The lockfile is always committed or rolled back.
 */
extern void update_index_if_able(struct index_state *, struct lock_file *);

extern int hold_locked_index(struct lock_file *, int);
extern void set_alternate_index_output(const char *);

extern int verify_index_checksum;
extern int verify_ce_order;

/* Environment bits from configuration mechanism */
extern int trust_executable_bit;
extern int trust_ctime;
extern int check_stat;
extern int quote_path_fully;
extern int has_symlinks;
extern int minimum_abbrev, default_abbrev;
extern int ignore_case;
extern int assume_unchanged;
extern int prefer_symlink_refs;
extern int warn_ambiguous_refs;
extern int warn_on_object_refname_ambiguity;
extern const char *apply_default_whitespace;
extern const char *apply_default_ignorewhitespace;
extern const char *git_attributes_file;
extern const char *git_hooks_path;
extern int zlib_compression_level;
extern int core_compression_level;
extern int pack_compression_level;
extern size_t packed_git_window_size;
extern size_t packed_git_limit;
extern size_t delta_base_cache_limit;
extern unsigned long big_file_threshold;
extern unsigned long pack_size_limit_cfg;

/*
 * Accessors for the core.sharedrepository config which lazy-load the value
 * from the config (if not already set). The "reset" function can be
 * used to unset "set" or cached value, meaning that the value will be loaded
 * fresh from the config file on the next call to get_shared_repository().
 */
void set_shared_repository(int value);
int get_shared_repository(void);
void reset_shared_repository(void);

/*
 * Do replace refs need to be checked this run?  This variable is
 * initialized to true unless --no-replace-object is used or
 * $GIT_NO_REPLACE_OBJECTS is set, but is set to false by some
 * commands that do not want replace references to be active.
 */
extern int read_replace_refs;
extern char *git_replace_ref_base;

extern int fsync_object_files;
extern int core_preload_index;
extern int core_apply_sparse_checkout;
extern int precomposed_unicode;
extern int protect_hfs;
extern int protect_ntfs;
extern const char *core_fsmonitor;

/*
 * Include broken refs in all ref iterations, which will
 * generally choke dangerous operations rather than letting
 * them silently proceed without taking the broken ref into
 * account.
 */
extern int ref_paranoia;

/*
 * Returns the boolean value of $GIT_OPTIONAL_LOCKS (or the default value).
 */
int use_optional_locks(void);

/*
 * The character that begins a commented line in user-editable file
 * that is subject to stripspace.
 */
extern char comment_line_char;
extern int auto_comment_line_char;

enum log_refs_config {
	LOG_REFS_UNSET = -1,
	LOG_REFS_NONE = 0,
	LOG_REFS_NORMAL,
	LOG_REFS_ALWAYS
};
extern enum log_refs_config log_all_ref_updates;

enum rebase_setup_type {
	AUTOREBASE_NEVER = 0,
	AUTOREBASE_LOCAL,
	AUTOREBASE_REMOTE,
	AUTOREBASE_ALWAYS
};

enum push_default_type {
	PUSH_DEFAULT_NOTHING = 0,
	PUSH_DEFAULT_MATCHING,
	PUSH_DEFAULT_SIMPLE,
	PUSH_DEFAULT_UPSTREAM,
	PUSH_DEFAULT_CURRENT,
	PUSH_DEFAULT_UNSPECIFIED
};

extern enum rebase_setup_type autorebase;
extern enum push_default_type push_default;

enum object_creation_mode {
	OBJECT_CREATION_USES_HARDLINKS = 0,
	OBJECT_CREATION_USES_RENAMES = 1
};

extern enum object_creation_mode object_creation_mode;

extern char *notes_ref_name;

extern int grafts_replace_parents;

/*
 * GIT_REPO_VERSION is the version we write by default. The
 * _READ variant is the highest number we know how to
 * handle.
 */
#define GIT_REPO_VERSION 0
#define GIT_REPO_VERSION_READ 1
extern int repository_format_precious_objects;
extern char *repository_format_partial_clone;
extern const char *core_partial_clone_filter_default;
extern int repository_format_worktree_config;

struct repository_format {
	int version;
	int precious_objects;
	char *partial_clone; /* value of extensions.partialclone */
	int worktree_config;
	int is_bare;
	int hash_algo;
	char *work_tree;
	struct string_list unknown_extensions;
};

/*
 * Read the repository format characteristics from the config file "path" into
 * "format" struct. Returns the numeric version. On error, -1 is returned,
 * format->version is set to -1, and all other fields in the struct are
 * undefined.
 */
int read_repository_format(struct repository_format *format, const char *path);

/*
 * Verify that the repository described by repository_format is something we
 * can read. If it is, return 0. Otherwise, return -1, and "err" will describe
 * any errors encountered.
 */
int verify_repository_format(const struct repository_format *format,
			     struct strbuf *err);