git/merge-recursive.c

/*
 * Recursive Merge algorithm stolen from git-merge-recursive.py by
 * Fredrik Kuivinen.
 * The thieves were Alex Riesen and Johannes Schindelin, in June/July 2006
 */
#include <stdarg.h>
#include <string.h>
#include <assert.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <time.h>
#include "cache.h"
#include "cache-tree.h"
#include "commit.h"
#include "blob.h"
#include "tree-walk.h"
#include "diff.h"
#include "diffcore.h"
#include "run-command.h"
#include "tag.h"

#include "path-list.h"

/*#define DEBUG*/

#ifdef DEBUG
#define debug(args, ...) fprintf(stderr, args, ## __VA_ARGS__)
#else
#define debug(args, ...)
#endif

#ifdef DEBUG
#include "quote.h"
static void show_ce_entry(const char *tag, struct cache_entry *ce)
{
	if (tag && *tag &&
	    (ce->ce_flags & htons(CE_VALID))) {
		static char alttag[4];
		memcpy(alttag, tag, 3);
		if (isalpha(tag[0]))
			alttag[0] = tolower(tag[0]);
		else if (tag[0] == '?')
			alttag[0] = '!';
		else {
			alttag[0] = 'v';
			alttag[1] = tag[0];
			alttag[2] = ' ';
			alttag[3] = 0;
		}
		tag = alttag;
	}

	fprintf(stderr,"%s%06o %s %d\t",
			tag,
			ntohl(ce->ce_mode),
			sha1_to_hex(ce->sha1),
			ce_stage(ce));
	write_name_quoted("", 0, ce->name,
			'\n', stderr);
	fputc('\n', stderr);
}

static void ls_files() {
	int i;
	for (i = 0; i < active_nr; i++) {
		struct cache_entry *ce = active_cache[i];
		show_ce_entry("", ce);
	}
	fprintf(stderr, "---\n");
}
#endif

/*
 * A virtual commit has
 * - (const char *)commit->util set to the name, and
 * - *(int *)commit->object.sha1 set to the virtual id.
 */
static const char *commit_title(struct commit *commit, int *len)
{
	const char *s = "(null commit)";
	*len = strlen(s);

	if ( commit->util ) {
		s = commit->util;
		*len = strlen(s);
	} else {
		if ( parse_commit(commit) != 0 ) {
			s = "(bad commit)";
			*len = strlen(s);
		} else {
			s = commit->buffer;
			char prev = '\0';
			while ( *s ) {
				if ( '\n' == prev && '\n' == *s ) {
					++s;
					break;
				}
				prev = *s++;
			}
			*len = 0;
			while ( s[*len] && '\n' != s[*len] )
				++(*len);
		}
	}
	return s;
}

static const char *commit_hex_sha1(const struct commit *commit)
{
	return commit->util ? "virtual" : commit ?
		sha1_to_hex(commit->object.sha1) : "undefined";
}

static unsigned commit_list_count(const struct commit_list *l)
{
	unsigned c = 0;
	for (; l; l = l->next )
		c++;
	return c;
}

static struct commit *make_virtual_commit(struct tree *tree, const char *comment)
{
	struct commit *commit = xcalloc(1, sizeof(struct commit));
	static unsigned virtual_id = 1;
	commit->tree = tree;
	commit->util = (void*)comment;
	*(int*)commit->object.sha1 = virtual_id++;
	return commit;
}

/*
 * TODO: we should not have to copy the SHA1s around, but rather reference
 * them. That way, sha_eq() is just sha1 == sha2.
 */
static int sha_eq(const unsigned char *a, const unsigned char *b)
{
	if ( !a && !b )
		return 2;
	return a && b && memcmp(a, b, 20) == 0;
}

static void memswp(void *p1, void *p2, unsigned n)
{
	unsigned char *a = p1, *b = p2;
	while ( n-- ) {
		*a ^= *b;
		*b ^= *a;
		*a ^= *b;
		++a;
		++b;
	}
}

/*
 * TODO: we should convert the merge_result users to
 * 	int blabla(..., struct commit **result)
 * like everywhere else in git.
 * Same goes for merge_tree_result and merge_file_info.
 */
struct merge_result
{
	struct commit *commit;
	unsigned clean:1;
};

struct merge_tree_result
{
	struct tree *tree;
	unsigned clean:1;
};

/*
 * TODO: check if we can just reuse the active_cache structure: it is already
 * sorted (by name, stage).
 * Only problem: do not write it when flushing the cache.
 */
struct stage_data
{
	struct
	{
		unsigned mode;
		unsigned char sha[20];
	} stages[4];
	unsigned processed:1;
};

static struct path_list currentFileSet = {NULL, 0, 0, 1};
static struct path_list currentDirectorySet = {NULL, 0, 0, 1};

static int output_indent = 0;

static void output(const char *fmt, ...)
{
	va_list args;
	int i;
	for ( i = output_indent; i--; )
		fputs("  ", stdout);
	va_start(args, fmt);
	vfprintf(stdout, fmt, args);
	va_end(args);
	fputc('\n', stdout);
}

static const char *original_index_file;
static const char *temporary_index_file;
static int cache_dirty = 0;

static int flush_cache()
{
	/* flush temporary index */
	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
	int fd = hold_lock_file_for_update(lock, getenv("GIT_INDEX_FILE"));
	if (fd < 0)
		die("could not lock %s", temporary_index_file);
	if (write_cache(fd, active_cache, active_nr) ||
			close(fd) || commit_lock_file(lock))
		die ("unable to write %s", getenv("GIT_INDEX_FILE"));
	discard_cache();
	cache_dirty = 0;
	return 0;
}

static void setup_index(int temp)
{
	const char *idx = temp ? temporary_index_file: original_index_file;
	if (cache_dirty)
		die("fatal: cache changed flush_cache();");
	unlink(temporary_index_file);
	setenv("GIT_INDEX_FILE", idx, 1);
	discard_cache();
}

static struct cache_entry *make_cache_entry(unsigned int mode,
		const unsigned char *sha1, const char *path, int stage, int refresh)
{
	int size, len;
	struct cache_entry *ce;

	if (!verify_path(path))
		return NULL;

	len = strlen(path);
	size = cache_entry_size(len);
	ce = xcalloc(1, size);

	memcpy(ce->sha1, sha1, 20);
	memcpy(ce->name, path, len);
	ce->ce_flags = create_ce_flags(len, stage);
	ce->ce_mode = create_ce_mode(mode);

	if (refresh)
		return refresh_cache_entry(ce, 0);

	return ce;
}

static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
		const char *path, int stage, int refresh, int options)
{
	struct cache_entry *ce;
	if (!cache_dirty)
		read_cache_from(getenv("GIT_INDEX_FILE"));
	cache_dirty++;
	ce = make_cache_entry(mode, sha1 ? sha1 : null_sha1, path, stage, refresh);
	if (!ce)
		return error("cache_addinfo failed: %s", strerror(cache_errno));
	return add_cache_entry(ce, options);
}

/*
 * This is a global variable which is used in a number of places but
 * only written to in the 'merge' function.
 *
 * index_only == 1    => Don't leave any non-stage 0 entries in the cache and
 *                       don't update the working directory.
 *               0    => Leave unmerged entries in the cache and update
 *                       the working directory.
 */
static int index_only = 0;

/*
 * TODO: this can be streamlined by refactoring builtin-read-tree.c
 */
static int git_read_tree(const struct tree *tree)
{
#if 0
	fprintf(stderr, "GIT_INDEX_FILE='%s' git-read-tree %s\n",
		getenv("GIT_INDEX_FILE"),
		sha1_to_hex(tree->object.sha1));
#endif
	const char *argv[] = { "git-read-tree", NULL, NULL, };
	if (cache_dirty)
		die("read-tree with dirty cache");
	argv[1] = sha1_to_hex(tree->object.sha1);
	int rc = run_command_v(2, argv);
	return rc < 0 ? -1: rc;
}

/*
 * TODO: this can be streamlined by refactoring builtin-read-tree.c
 */
static int git_merge_trees(const char *update_arg,
			   struct tree *common,
			   struct tree *head,
			   struct tree *merge)
{
#if 0
	fprintf(stderr, "GIT_INDEX_FILE='%s' git-read-tree %s -m %s %s %s\n",
		getenv("GIT_INDEX_FILE"),
		update_arg,
		sha1_to_hex(common->object.sha1),
		sha1_to_hex(head->object.sha1),
		sha1_to_hex(merge->object.sha1));
#endif
	const char *argv[] = {
		"git-read-tree", NULL, "-m", NULL, NULL, NULL,
		NULL,
	};
	if (cache_dirty)
		flush_cache();
	argv[1] = update_arg;
	argv[3] = sha1_to_hex(common->object.sha1);
	argv[4] = sha1_to_hex(head->object.sha1);
	argv[5] = sha1_to_hex(merge->object.sha1);
	int rc = run_command_v(6, argv);
	return rc < 0 ? -1: rc;
}

/*
 * TODO: this can be streamlined by refactoring builtin-write-tree.c
 */
static struct tree *git_write_tree()
{
#if 0
	fprintf(stderr, "GIT_INDEX_FILE='%s' git-write-tree\n",
		getenv("GIT_INDEX_FILE"));
#endif
	if (cache_dirty)
		flush_cache();
	FILE *fp = popen("git-write-tree 2>/dev/null", "r");
	char buf[41];
	unsigned char sha1[20];
	int ch;
	unsigned i = 0;
	while ( (ch = fgetc(fp)) != EOF )
		if ( i < sizeof(buf)-1 && ch >= '0' && ch <= 'f' )
			buf[i++] = ch;
		else
			break;
	int rc = pclose(fp);
	if ( rc == -1 || WEXITSTATUS(rc) )
		return NULL;
	buf[i] = '\0';
	if ( get_sha1(buf, sha1) != 0 )
		return NULL;
	return lookup_tree(sha1);
}

/*
 * TODO: get rid of files_and_dirs; we do not use it except for
 * current_file_set and current_dir_set, which are global already.
 */
static struct
{
	struct path_list *files;
	struct path_list *dirs;
} files_and_dirs;

static int save_files_dirs(const unsigned char *sha1,
		const char *base, int baselen, const char *path,
		unsigned int mode, int stage)
{
	int len = strlen(path);
	char *newpath = malloc(baselen + len + 1);
	memcpy(newpath, base, baselen);
	memcpy(newpath + baselen, path, len);
	newpath[baselen + len] = '\0';

	if (S_ISDIR(mode))
		path_list_insert(newpath, files_and_dirs.dirs);
	else
		path_list_insert(newpath, files_and_dirs.files);
	free(newpath);

	return READ_TREE_RECURSIVE;
}

static int get_files_dirs(struct tree *tree,
			  struct path_list *files,
			  struct path_list *dirs)
{
	int n;
	files_and_dirs.files = files;
	files_and_dirs.dirs = dirs;
	debug("get_files_dirs ...\n");
	if (read_tree_recursive(tree, "", 0, 0, NULL, save_files_dirs) != 0) {
		debug("  get_files_dirs done (0)\n");
		return 0;
	}
	n = files->nr + dirs->nr;
	debug("  get_files_dirs done (%d)\n", n);
	return n;
}

/*
 * TODO: this wrapper is so small, we can use path_list_lookup directly.
 * Same goes for index_entry_get(), free_index_entries(), find_rename_bysrc(),
 * free_rename_entries().
 */
static struct stage_data *index_entry_find(struct path_list *ents,
					    const char *path)
{
	struct path_list_item *item = path_list_lookup(path, ents);
	if (item)
		return item->util;
	return NULL;
}

static struct stage_data *index_entry_get(struct path_list *ents,
					   const char *path)
{
	struct path_list_item *item = path_list_lookup(path, ents);

	if (item == NULL) {
		item = path_list_insert(path, ents);
		item->util = xcalloc(1, sizeof(struct stage_data));
	}
	return item->util;
}

/*
 * TODO: since the result of index_entry_from_db() is tucked into a
 * path_list anyway, this helper can do that already.
 */
/*
 * Returns a index_entry instance which doesn't have to correspond to
 * a real cache entry in Git's index.
 */
static struct stage_data *index_entry_from_db(const char *path,
					       struct tree *o,
					       struct tree *a,
					       struct tree *b)
{
	struct stage_data *e = xcalloc(1, sizeof(struct stage_data));
	get_tree_entry(o->object.sha1, path,
			e->stages[1].sha, &e->stages[1].mode);
	get_tree_entry(a->object.sha1, path,
			e->stages[2].sha, &e->stages[2].mode);
	get_tree_entry(b->object.sha1, path,
			e->stages[3].sha, &e->stages[3].mode);
	return e;
}

static void free_index_entries(struct path_list **ents)
{
	if (!*ents)
		return;

	path_list_clear(*ents, 1);
	free(*ents);
	*ents = NULL;
}

/*
 * Create a dictionary mapping file names to CacheEntry objects. The
 * dictionary contains one entry for every path with a non-zero stage entry.
 */
static struct path_list *get_unmerged()
{
	struct path_list *unmerged = xcalloc(1, sizeof(struct path_list));
	int i;

	unmerged->strdup_paths = 1;
	if (!cache_dirty) {
		read_cache_from(getenv("GIT_INDEX_FILE"));
		cache_dirty++;
	}
	for (i = 0; i < active_nr; i++) {
		struct cache_entry *ce = active_cache[i];
		if (!ce_stage(ce))
			continue;

		struct stage_data *e = index_entry_get(unmerged, ce->name);
		e->stages[ce_stage(ce)].mode = ntohl(ce->ce_mode);
		memcpy(e->stages[ce_stage(ce)].sha, ce->sha1, 20);
	}

	debug("  get_unmerged done\n");
	return unmerged;
}

struct rename
{
	struct diff_filepair *pair;
	struct stage_data *src_entry;
	struct stage_data *dst_entry;
	unsigned processed:1;
};

static struct rename *find_rename_bysrc(struct path_list *e,
					      const char *name)
{
	struct path_list_item *item = path_list_lookup(name, e);
	if (item)
		return item->util;
	return NULL;
}

static void free_rename_entries(struct path_list **list)
{
	if (!*list)
		return;

	path_list_clear(*list, 0);
	free(*list);
	*list = NULL;
}

/*
 * Get information of all renames which occured between 'oTree' and
 * 'tree'. We need the three trees in the merge ('oTree', 'aTree' and
 * 'bTree') to be able to associate the correct cache entries with
 * the rename information. 'tree' is always equal to either aTree or bTree.
 */
static struct path_list *get_renames(struct tree *tree,
					struct tree *oTree,
					struct tree *aTree,
					struct tree *bTree,
					struct path_list *entries)
{
#ifdef DEBUG
	time_t t = time(0);
	debug("getRenames ...\n");
#endif
	int i;
	struct path_list *renames = xcalloc(1, sizeof(struct path_list));
	struct diff_options opts;
	diff_setup(&opts);
	opts.recursive = 1;
	opts.detect_rename = DIFF_DETECT_RENAME;
	opts.output_format = DIFF_FORMAT_NO_OUTPUT;
	if (diff_setup_done(&opts) < 0)
		die("diff setup failed");
	diff_tree_sha1(oTree->object.sha1, tree->object.sha1, "", &opts);
	diffcore_std(&opts);
	for (i = 0; i < diff_queued_diff.nr; ++i) {
		struct rename *re;
		struct diff_filepair *pair = diff_queued_diff.queue[i];
		if (pair->status != 'R') {
			diff_free_filepair(pair);
			continue;
		}
		re = xmalloc(sizeof(*re));
		re->processed = 0;
		re->pair = pair;
		re->src_entry = index_entry_find(entries, re->pair->one->path);
		/* TODO: should it not be an error, if src_entry was found? */
		if ( !re->src_entry ) {
			re->src_entry = index_entry_from_db(re->pair->one->path,
					oTree, aTree, bTree);
			struct path_list_item *item =
				path_list_insert(re->pair->one->path, entries);
			item->util = re->src_entry;
		}
		re->dst_entry = index_entry_find(entries, re->pair->two->path);
		if ( !re->dst_entry ) {
			re->dst_entry = index_entry_from_db(re->pair->two->path,
					oTree, aTree, bTree);
			struct path_list_item *item =
				path_list_insert(re->pair->two->path, entries);
			item->util = re->dst_entry;
		}
		struct path_list_item *item = path_list_insert(pair->one->path, renames);
		item->util = re;
	}
	opts.output_format = DIFF_FORMAT_NO_OUTPUT;
	diff_queued_diff.nr = 0;
	diff_flush(&opts);
	debug("  getRenames done in %ld\n", time(0)-t);
	return renames;
}

/*
 * TODO: the code would be way nicer, if we had a struct containing just sha1 and mode.
 * In this particular case, we might get away reusing stage_data, no?
 */
int update_stages(const char *path,
		   unsigned char *osha, unsigned omode,
		   unsigned char *asha, unsigned amode,
		   unsigned char *bsha, unsigned bmode,
		   int clear /* =True */)
{
	int options = ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE;
	if ( clear )
		if (add_cacheinfo(0, null_sha1, path, 0, 0, options))
			return -1;
	if ( omode )
		if (add_cacheinfo(omode, osha, path, 1, 0, options))
			return -1;
	if ( amode )
		if (add_cacheinfo(omode, osha, path, 2, 0, options))
			return -1;
	if ( bmode )
		if (add_cacheinfo(omode, osha, path, 3, 0, options))
			return -1;
	return 0;
}

/*
 * TODO: there has to be a function in libgit doing this exact thing.
 */
static int remove_path(const char *name)
{
	int ret;
	char *slash;

	ret = unlink(name);
	if ( ret )
		return ret;
	int len = strlen(name);
	char *dirs = malloc(len+1);
	memcpy(dirs, name, len);
	dirs[len] = '\0';
	while ( (slash = strrchr(name, '/')) ) {
		*slash = '\0';
		len = slash - name;
		if ( rmdir(name) != 0 )
			break;
	}
	free(dirs);
	return ret;
}

/* General TODO: unC99ify the code: no declaration after code */
/* General TODO: no javaIfiCation: rename updateCache to update_cache */
/*
 * TODO: once we no longer call external programs, we'd probably be better of
 * not setting / getting the environment variable GIT_INDEX_FILE all the time.
 */
int remove_file(int clean, const char *path)
{
	int updateCache = index_only || clean;
	int updateWd = !index_only;

	if ( updateCache ) {
		if (!cache_dirty)
			read_cache_from(getenv("GIT_INDEX_FILE"));
		cache_dirty++;
		if (remove_file_from_cache(path))
			return -1;
	}
	if ( updateWd )
	{
		unlink(path);
		if ( errno != ENOENT || errno != EISDIR )
			return -1;
		remove_path(path);
	}
	return 0;
}

static char *unique_path(const char *path, const char *branch)
{
	char *newpath = xmalloc(strlen(path) + 1 + strlen(branch) + 8 + 1);
	strcpy(newpath, path);
	strcat(newpath, "~");
	char *p = newpath + strlen(newpath);
	strcpy(p, branch);
	for ( ; *p; ++p )
		if ( '/' == *p )
			*p = '_';
	int suffix = 0;
	struct stat st;
	while ( path_list_has_path(&currentFileSet, newpath) ||
		path_list_has_path(&currentDirectorySet, newpath) ||
		lstat(newpath, &st) == 0 ) {
		sprintf(p, "_%d", suffix++);
	}
	path_list_insert(newpath, &currentFileSet);
	return newpath;
}

/*
 * TODO: except for create_last, this so looks like
 * safe_create_leading_directories().
 */
static int mkdir_p(const char *path, unsigned long mode, int create_last)
{
	char *buf = strdup(path);
	char *p;

	for ( p = buf; *p; ++p ) {
		if ( *p != '/' )
			continue;
		*p = '\0';
		if (mkdir(buf, mode)) {
			int e = errno;
			if ( e == EEXIST ) {
				struct stat st;
				if ( !stat(buf, &st) && S_ISDIR(st.st_mode) )
					goto next; /* ok */
				errno = e;
			}
			free(buf);
			return -1;
		}
	next:
		*p = '/';
	}
	free(buf);
	if ( create_last && mkdir(path, mode) )
		return -1;
	return 0;
}

static void flush_buffer(int fd, const char *buf, unsigned long size)
{
	while (size > 0) {
		long ret = xwrite(fd, buf, size);
		if (ret < 0) {
			/* Ignore epipe */
			if (errno == EPIPE)
				break;
			die("merge-recursive: %s", strerror(errno));
		} else if (!ret) {
			die("merge-recursive: disk full?");
		}
		size -= ret;
		buf += ret;
	}
}

/* General TODO: reindent according to guide lines (no if ( blabla )) */
void update_file_flags(const unsigned char *sha,
		   unsigned mode,
		   const char *path,
		   int updateCache,
		   int updateWd)
{
	if ( index_only )
		updateWd = 0;

	if ( updateWd ) {
		char type[20];
		void *buf;
		unsigned long size;

		buf = read_sha1_file(sha, type, &size);
		if (!buf)
			die("cannot read object %s '%s'", sha1_to_hex(sha), path);
		if ( strcmp(type, blob_type) != 0 )
			die("blob expected for %s '%s'", sha1_to_hex(sha), path);

		if ( S_ISREG(mode) ) {
			if ( mkdir_p(path, 0777, 0 /* don't create last element */) )
				die("failed to create path %s: %s", path, strerror(errno));
			unlink(path);
			if ( mode & 0100 )
				mode = 0777;
			else
				mode = 0666;
			int fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, mode);
			if ( fd < 0 )
				die("failed to open %s: %s", path, strerror(errno));
			flush_buffer(fd, buf, size);
			close(fd);
		} else if ( S_ISLNK(mode) ) {
			char *linkTarget = malloc(size + 1);
			memcpy(linkTarget, buf, size);
			linkTarget[size] = '\0';
			mkdir_p(path, 0777, 0);
			symlink(linkTarget, path);
		} else
			die("do not know what to do with %06o %s '%s'",
			    mode, sha1_to_hex(sha), path);
	}
	if ( updateCache )
		add_cacheinfo(mode, sha, path, 0, updateWd, ADD_CACHE_OK_TO_ADD);
}

/* TODO: is this often used? if not, do direct call */
void update_file(int clean,
		const unsigned char *sha,
		unsigned mode,
		const char *path)
{
	update_file_flags(sha, mode, path, index_only || clean, !index_only);
}

/* Low level file merging, update and removal */

struct merge_file_info
{
	unsigned char sha[20];
	unsigned mode;
	unsigned clean:1,
		 merge:1;
};

static char *git_unpack_file(const unsigned char *sha1, char *path)
{
	void *buf;
	char type[20];
	unsigned long size;
	int fd;

	buf = read_sha1_file(sha1, type, &size);
	if (!buf || strcmp(type, blob_type))
		die("unable to read blob object %s", sha1_to_hex(sha1));

	strcpy(path, ".merge_file_XXXXXX");
	fd = mkstemp(path);
	if (fd < 0)
		die("unable to create temp-file");
	flush_buffer(fd, buf, size);
	close(fd);
	return path;
}

/*
 * TODO: the signature would be much more efficient using stage_data
 */
static struct merge_file_info merge_file(const char *oPath,
					 const unsigned char *oSha,
					 unsigned oMode,
					 const char *aPath,
					 const unsigned char *aSha,
					 unsigned aMode,
					 const char *bPath,
					 const unsigned char *bSha,
					 unsigned bMode,
					 const char *branch1Name,
					 const char *branch2Name)
{
	struct merge_file_info result;
	result.merge = 0;
	result.clean = 1;

	if ( (S_IFMT & aMode) != (S_IFMT & bMode) ) {
		result.clean = 0;
		if ( S_ISREG(aMode) ) {
			result.mode = aMode;
			memcpy(result.sha, aSha, 20);
		} else {
			result.mode = bMode;
			memcpy(result.sha, bSha, 20);
		}
	} else {
		if ( memcmp(aSha, oSha, 20) != 0 && memcmp(bSha, oSha, 20) != 0 )
			result.merge = 1;

		result.mode = aMode == oMode ? bMode: aMode;

		if ( memcmp(aSha, oSha, 20) == 0 )
			memcpy(result.sha, bSha, 20);
		else if ( memcmp(bSha, oSha, 20) == 0 )
			memcpy(result.sha, aSha, 20);
		else if ( S_ISREG(aMode) ) {

			int code = 1;
			char orig[PATH_MAX];
			char src1[PATH_MAX];
			char src2[PATH_MAX];

			git_unpack_file(oSha, orig);
			git_unpack_file(aSha, src1);
			git_unpack_file(bSha, src2);

			const char *argv[] = {
				"merge", "-L", NULL, "-L", NULL, "-L", NULL,
				src1, orig, src2,
				NULL
			};
			char *la, *lb, *lo;
			argv[2] = la = strdup(mkpath("%s/%s", branch1Name, aPath));
			argv[6] = lb = strdup(mkpath("%s/%s", branch2Name, bPath));
			argv[4] = lo = strdup(mkpath("orig/%s", oPath));

#if 0
			printf("%s %s %s %s %s %s %s %s %s %s\n",
			       argv[0], argv[1], argv[2], argv[3], argv[4],
			       argv[5], argv[6], argv[7], argv[8], argv[9]);
#endif
			code = run_command_v(10, argv);

			free(la);
			free(lb);
			free(lo);
			if ( code && code < -256 ) {
				die("Failed to execute 'merge'. merge(1) is used as the "
				    "file-level merge tool. Is 'merge' in your path?");
			}
			struct stat st;
			int fd = open(src1, O_RDONLY);
			if (fd < 0 || fstat(fd, &st) < 0 ||
					index_fd(result.sha, fd, &st, 1,
						"blob"))
				die("Unable to add %s to database", src1);
			close(fd);

			unlink(orig);
			unlink(src1);
			unlink(src2);

			result.clean = WEXITSTATUS(code) == 0;
		} else {
			if ( !(S_ISLNK(aMode) || S_ISLNK(bMode)) )
				die("cannot merge modes?");

			memcpy(result.sha, aSha, 20);

			if ( memcmp(aSha, bSha, 20) != 0 )
				result.clean = 0;
		}
	}

	return result;
}

static void conflict_rename_rename(struct rename *ren1,
				   const char *branch1,
				   struct rename *ren2,
				   const char *branch2)
{
	char *del[2];
	int delp = 0;
	const char *ren1_dst = ren1->pair->two->path;
	const char *ren2_dst = ren2->pair->two->path;
	const char *dstName1 = ren1_dst;
	const char *dstName2 = ren2_dst;
	if (path_list_has_path(&currentDirectorySet, ren1_dst)) {
		dstName1 = del[delp++] = unique_path(ren1_dst, branch1);
		output("%s is a directory in %s adding as %s instead",
		       ren1_dst, branch2, dstName1);
		remove_file(0, ren1_dst);
	}
	if (path_list_has_path(&currentDirectorySet, ren2_dst)) {
		dstName2 = del[delp++] = unique_path(ren2_dst, branch2);
		output("%s is a directory in %s adding as %s instead",
		       ren2_dst, branch1, dstName2);
		remove_file(0, ren2_dst);
	}
	update_stages(dstName1,
		      NULL, 0,
		      ren1->pair->two->sha1, ren1->pair->two->mode,
		      NULL, 0,
		      1 /* clear */);
	update_stages(dstName2,
		      NULL, 0,
		      NULL, 0,
		      ren2->pair->two->sha1, ren2->pair->two->mode,
		      1 /* clear */);
	while ( delp-- )
		free(del[delp]);
}

static void conflict_rename_dir(struct rename *ren1,
				const char *branch1)
{
	char *newPath = unique_path(ren1->pair->two->path, branch1);
	output("Renaming %s to %s instead", ren1->pair->one->path, newPath);
	remove_file(0, ren1->pair->two->path);
	update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, newPath);
	free(newPath);
}

static void conflict_rename_rename_2(struct rename *ren1,
				     const char *branch1,
				     struct rename *ren2,
				     const char *branch2)
{
	char *newPath1 = unique_path(ren1->pair->two->path, branch1);
	char *newPath2 = unique_path(ren2->pair->two->path, branch2);
	output("Renaming %s to %s and %s to %s instead",
	       ren1->pair->one->path, newPath1,
	       ren2->pair->one->path, newPath2);
	remove_file(0, ren1->pair->two->path);
	update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, newPath1);
	update_file(0, ren2->pair->two->sha1, ren2->pair->two->mode, newPath2);
	free(newPath2);
	free(newPath1);
}

/* General TODO: get rid of all the debug messages */
static int process_renames(struct path_list *renamesA,
			   struct path_list *renamesB,
			   const char *branchNameA,
			   const char *branchNameB)
{
	int cleanMerge = 1, i;
	struct path_list srcNames = {NULL, 0, 0, 0}, byDstA = {NULL, 0, 0, 0}, byDstB = {NULL, 0, 0, 0};
	const struct rename *sre;

	/*
	 * TODO: think about a saner way to do this.
	 * Since both renamesA and renamesB are sorted, it should
	 * be much more efficient to traverse both simultaneously,
	 * only byDstA and byDstB should be needed.
	 */
	debug("processRenames...\n");
	for (i = 0; i < renamesA->nr; i++) {
		sre = renamesA->items[i].util;
		path_list_insert(sre->pair->one->path, &srcNames);
		path_list_insert(sre->pair->two->path, &byDstA)->util
			= sre->dst_entry;
	}
	for (i = 0; i < renamesB->nr; i++) {
		sre = renamesB->items[i].util;
		path_list_insert(sre->pair->one->path, &srcNames);
		path_list_insert(sre->pair->two->path, &byDstB)->util
			= sre->dst_entry;
	}

	for (i = 0; i < srcNames.nr; i++) {
		char *src = srcNames.items[i].path;
		struct path_list *renames1, *renames2, *renames2Dst;
		struct rename *ren1, *ren2;
		const char *branchName1, *branchName2;
		ren1 = find_rename_bysrc(renamesA, src);
		ren2 = find_rename_bysrc(renamesB, src);
		/* TODO: refactor, so that 1/2 are not needed */
		if ( ren1 ) {
			renames1 = renamesA;
			renames2 = renamesB;
			renames2Dst = &byDstB;
			branchName1 = branchNameA;
			branchName2 = branchNameB;
		} else {
			renames1 = renamesB;
			renames2 = renamesA;
			renames2Dst = &byDstA;
			branchName1 = branchNameB;
			branchName2 = branchNameA;
			struct rename *tmp = ren2;
			ren2 = ren1;
			ren1 = tmp;
		}

		ren1->dst_entry->processed = 1;
		ren1->src_entry->processed = 1;

		if ( ren1->processed )
			continue;
		ren1->processed = 1;

		const char *ren1_src = ren1->pair->one->path;
		const char *ren1_dst = ren1->pair->two->path;

		if ( ren2 ) {
			const char *ren2_src = ren2->pair->one->path;
			const char *ren2_dst = ren2->pair->two->path;
			/* Renamed in 1 and renamed in 2 */
			if (strcmp(ren1_src, ren2_src) != 0)
				die("ren1.src != ren2.src");
			ren2->dst_entry->processed = 1;
			ren2->processed = 1;
			if (strcmp(ren1_dst, ren2_dst) != 0) {
				cleanMerge = 0;
				output("CONFLICT (rename/rename): "
				       "Rename %s->%s in branch %s "
				       "rename %s->%s in %s",
				       src, ren1_dst, branchName1,
				       src, ren2_dst, branchName2);
				conflict_rename_rename(ren1, branchName1, ren2, branchName2);
			} else {
				remove_file(1, ren1_src);
				struct merge_file_info mfi;
				mfi = merge_file(ren1_src,
						 ren1->pair->one->sha1,
						 ren1->pair->one->mode,
						 ren1_dst,
						 ren1->pair->two->sha1,
						 ren1->pair->two->mode,
						 ren2_dst,
						 ren2->pair->two->sha1,
						 ren2->pair->two->mode,
						 branchName1,
						 branchName2);
				if ( mfi.merge || !mfi.clean )
					output("Renaming %s->%s", src, ren1_dst);

				if ( mfi.merge )
					output("Auto-merging %s", ren1_dst);

				if ( !mfi.clean ) {
					output("CONFLICT (content): merge conflict in %s",
					       ren1_dst);
					cleanMerge = 0;

					if ( !index_only )
						update_stages(ren1_dst,
							      ren1->pair->one->sha1,
							      ren1->pair->one->mode,
							      ren1->pair->two->sha1,
							      ren1->pair->two->mode,
							      ren2->pair->two->sha1,
							      ren2->pair->two->mode,
							      1 /* clear */);
				}
				update_file(mfi.clean, mfi.sha, mfi.mode, ren1_dst);
			}
		} else {
			/* Renamed in 1, maybe changed in 2 */
			remove_file(1, ren1_src);

			unsigned char srcShaOtherBranch[20], dstShaOtherBranch[20];
			unsigned srcModeOtherBranch, dstModeOtherBranch;

			int stage = renamesA == renames1 ? 3: 2;

			memcpy(srcShaOtherBranch, ren1->src_entry->stages[stage].sha, 20);
			srcModeOtherBranch = ren1->src_entry->stages[stage].mode;

			memcpy(dstShaOtherBranch, ren1->dst_entry->stages[stage].sha, 20);
			dstModeOtherBranch = ren1->dst_entry->stages[stage].mode;

			int tryMerge = 0;
			char *newPath;

			if (path_list_has_path(&currentDirectorySet, ren1_dst)) {
				cleanMerge = 0;
				output("CONFLICT (rename/directory): Rename %s->%s in %s "
				       " directory %s added in %s",
				       ren1_src, ren1_dst, branchName1,
				       ren1_dst, branchName2);
				conflict_rename_dir(ren1, branchName1);
			} else if ( memcmp(srcShaOtherBranch, null_sha1, 20) == 0 ) {
				cleanMerge = 0;
				output("CONFLICT (rename/delete): Rename %s->%s in %s "
				       "and deleted in %s",
				       ren1_src, ren1_dst, branchName1,
				       branchName2);
				update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, ren1_dst);
			} else if ( memcmp(dstShaOtherBranch, null_sha1, 20) != 0 ) {
				cleanMerge = 0;
				tryMerge = 1;
				output("CONFLICT (rename/add): Rename %s->%s in %s. "
				       "%s added in %s",
				       ren1_src, ren1_dst, branchName1,
				       ren1_dst, branchName2);
				newPath = unique_path(ren1_dst, branchName2);
				output("Adding as %s instead", newPath);
				update_file(0, dstShaOtherBranch, dstModeOtherBranch, newPath);
			} else if ( (ren2 = find_rename_bysrc(renames2Dst, ren1_dst)) ) {
				cleanMerge = 0;
				ren2->processed = 1;
				output("CONFLICT (rename/rename): Rename %s->%s in %s. "
				       "Rename %s->%s in %s",
				       ren1_src, ren1_dst, branchName1,
				       ren2->pair->one->path, ren2->pair->two->path, branchName2);
				conflict_rename_rename_2(ren1, branchName1, ren2, branchName2);
			} else
				tryMerge = 1;

			if ( tryMerge ) {
				const char *oname = ren1_src;
				const char *aname = ren1_dst;
				const char *bname = ren1_src;
				unsigned char osha[20], asha[20], bsha[20];
				unsigned omode = ren1->pair->one->mode;
				unsigned amode = ren1->pair->two->mode;
				unsigned bmode = srcModeOtherBranch;
				memcpy(osha, ren1->pair->one->sha1, 20);
				memcpy(asha, ren1->pair->two->sha1, 20);
				memcpy(bsha, srcShaOtherBranch, 20);
				const char *aBranch = branchName1;
				const char *bBranch = branchName2;

				if ( renamesA != renames1 ) {
					memswp(&aname, &bname, sizeof(aname));
					memswp(asha, bsha, 20);
					memswp(&aBranch, &bBranch, sizeof(aBranch));
				}
				struct merge_file_info mfi;
				mfi = merge_file(oname, osha, omode,
						 aname, asha, amode,
						 bname, bsha, bmode,
						 aBranch, bBranch);

				if ( mfi.merge || !mfi.clean )
					output("Renaming %s => %s", ren1_src, ren1_dst);
				if ( mfi.merge )
					output("Auto-merging %s", ren1_dst);
				if ( !mfi.clean ) {
					output("CONFLICT (rename/modify): Merge conflict in %s",
					       ren1_dst);
					cleanMerge = 0;

					if ( !index_only )
						update_stages(ren1_dst,
							      osha, omode,
							      asha, amode,
							      bsha, bmode,
							      1 /* clear */);
				}
				update_file(mfi.clean, mfi.sha, mfi.mode, ren1_dst);
			}
		}
	}
	path_list_clear(&srcNames, 0);
	debug("  processRenames done\n");

	if (cache_dirty)
		flush_cache();
	return cleanMerge;
}

static unsigned char *has_sha(const unsigned char *sha)
{
	return memcmp(sha, null_sha1, 20) == 0 ? NULL: (unsigned char *)sha;
}

/* Per entry merge function */
static int process_entry(const char *path, struct stage_data *entry,
			 const char *branch1Name,
			 const char *branch2Name)
{
	/*
	printf("processing entry, clean cache: %s\n", index_only ? "yes": "no");
	print_index_entry("\tpath: ", entry);
	*/
	int cleanMerge = 1;
	unsigned char *oSha = has_sha(entry->stages[1].sha);
	unsigned char *aSha = has_sha(entry->stages[2].sha);
	unsigned char *bSha = has_sha(entry->stages[3].sha);
	unsigned oMode = entry->stages[1].mode;
	unsigned aMode = entry->stages[2].mode;
	unsigned bMode = entry->stages[3].mode;

	if ( oSha && (!aSha || !bSha) ) {
		/* Case A: Deleted in one */
		if ( (!aSha && !bSha) ||
		     (sha_eq(aSha, oSha) && !bSha) ||
		     (!aSha && sha_eq(bSha, oSha)) ) {
			/* Deleted in both or deleted in one and
			 * unchanged in the other */
			if ( aSha )
				output("Removing %s", path);
			remove_file(1, path);
		} else {
			/* Deleted in one and changed in the other */
			cleanMerge = 0;
			if ( !aSha ) {
				output("CONFLICT (delete/modify): %s deleted in %s "
				       "and modified in %s. Version %s of %s left in tree.",
				       path, branch1Name,
				       branch2Name, branch2Name, path);
				update_file(0, bSha, bMode, path);
			} else {
				output("CONFLICT (delete/modify): %s deleted in %s "
				       "and modified in %s. Version %s of %s left in tree.",
				       path, branch2Name,
				       branch1Name, branch1Name, path);
				update_file(0, aSha, aMode, path);
			}
		}

	} else if ( (!oSha && aSha && !bSha) ||
		    (!oSha && !aSha && bSha) ) {
		/* Case B: Added in one. */
		const char *addBranch;
		const char *otherBranch;
		unsigned mode;
		const unsigned char *sha;
		const char *conf;

		if ( aSha ) {
			addBranch = branch1Name;
			otherBranch = branch2Name;
			mode = aMode;
			sha = aSha;
			conf = "file/directory";
		} else {
			addBranch = branch2Name;
			otherBranch = branch1Name;
			mode = bMode;
			sha = bSha;
			conf = "directory/file";
		}
		if ( path_list_has_path(&currentDirectorySet, path) ) {
			cleanMerge = 0;
			const char *newPath = unique_path(path, addBranch);
			output("CONFLICT (%s): There is a directory with name %s in %s. "
			       "Adding %s as %s",
			       conf, path, otherBranch, path, newPath);
			remove_file(0, path);
			update_file(0, sha, mode, newPath);
		} else {
			output("Adding %s", path);
			update_file(1, sha, mode, path);
		}
	} else if ( !oSha && aSha && bSha ) {
		/* Case C: Added in both (check for same permissions). */
		if ( sha_eq(aSha, bSha) ) {
			if ( aMode != bMode ) {
				cleanMerge = 0;
				output("CONFLICT: File %s added identically in both branches, "
				       "but permissions conflict %06o->%06o",
				       path, aMode, bMode);
				output("CONFLICT: adding with permission: %06o", aMode);
				update_file(0, aSha, aMode, path);
			} else {
				/* This case is handled by git-read-tree */
				assert(0 && "This case must be handled by git-read-tree");
			}
		} else {
			cleanMerge = 0;
			const char *newPath1 = unique_path(path, branch1Name);
			const char *newPath2 = unique_path(path, branch2Name);
			output("CONFLICT (add/add): File %s added non-identically "
			       "in both branches. Adding as %s and %s instead.",
			       path, newPath1, newPath2);
			remove_file(0, path);
			update_file(0, aSha, aMode, newPath1);
			update_file(0, bSha, bMode, newPath2);
		}

	} else if ( oSha && aSha && bSha ) {
		/* case D: Modified in both, but differently. */
		output("Auto-merging %s", path);
		struct merge_file_info mfi;
		mfi = merge_file(path, oSha, oMode,
				 path, aSha, aMode,
				 path, bSha, bMode,
				 branch1Name, branch2Name);

		if ( mfi.clean )
			update_file(1, mfi.sha, mfi.mode, path);
		else {
			cleanMerge = 0;
			output("CONFLICT (content): Merge conflict in %s", path);

			if ( index_only )
				update_file(0, mfi.sha, mfi.mode, path);
			else
				update_file_flags(mfi.sha, mfi.mode, path,
					      0 /* updateCache */, 1 /* updateWd */);
		}
	} else
		die("Fatal merge failure, shouldn't happen.");

	if (cache_dirty)
		flush_cache();

	return cleanMerge;
}

static struct merge_tree_result merge_trees(struct tree *head,
					    struct tree *merge,
					    struct tree *common,
					    const char *branch1Name,
					    const char *branch2Name)
{
	int code;
	struct merge_tree_result result = { NULL, 0 };
	if ( !memcmp(common->object.sha1, merge->object.sha1, 20) ) {
		output("Already uptodate!");
		result.tree = head;
		result.clean = 1;
		return result;
	}

	debug("merge_trees ...\n");
	code = git_merge_trees(index_only ? "-i": "-u", common, head, merge);

	if ( code != 0 )
		die("merging of trees %s and %s failed",
		    sha1_to_hex(head->object.sha1),
		    sha1_to_hex(merge->object.sha1));

	result.tree = git_write_tree();

	if ( !result.tree ) {
		path_list_clear(&currentFileSet, 1);
		path_list_clear(&currentDirectorySet, 1);
		get_files_dirs(head, &currentFileSet, &currentDirectorySet);
		get_files_dirs(merge, &currentFileSet, &currentDirectorySet);

		struct path_list *entries = get_unmerged();
		struct path_list *re_head, *re_merge;
		re_head  = get_renames(head, common, head, merge, entries);
		re_merge = get_renames(merge, common, head, merge, entries);
		result.clean = process_renames(re_head, re_merge,
					       branch1Name, branch2Name);
		debug("\tprocessing entries...\n");
		int i;
		for (i = 0; i < entries->nr; i++) {
			const char *path = entries->items[i].path;
			struct stage_data *e = entries->items[i].util;
			if (e->processed)
				continue;
			if (!process_entry(path, e, branch1Name, branch2Name))
				result.clean = 0;
		}

		free_rename_entries(&re_merge);
		free_rename_entries(&re_head);
		free_index_entries(&entries);

		if (result.clean || index_only)
			result.tree = git_write_tree();
		else
			result.tree = NULL;
		debug("\t  processing entries done\n");
	} else {
		result.clean = 1;
		printf("merging of trees %s and %s resulted in %s\n",
		       sha1_to_hex(head->object.sha1),
		       sha1_to_hex(merge->object.sha1),
		       sha1_to_hex(result.tree->object.sha1));
	}

	debug("  merge_trees done\n");
	return result;
}

/*
 * Merge the commits h1 and h2, return the resulting virtual
 * commit object and a flag indicating the cleaness of the merge.
 */
static
struct merge_result merge(struct commit *h1,
			  struct commit *h2,
			  const char *branch1Name,
			  const char *branch2Name,
			  int callDepth /* =0 */,
			  struct commit *ancestor /* =None */)
{
	struct merge_result result = { NULL, 0 };
	const char *msg;
	int msglen;
	struct commit_list *ca = NULL, *iter;
	struct commit *mergedCA;
	struct merge_tree_result mtr;

	output("Merging:");
	msg = commit_title(h1, &msglen);
	/* TODO: refactor. we always show the sha1 with the title */
	output("%s %.*s", commit_hex_sha1(h1), msglen, msg);
	msg = commit_title(h2, &msglen);
	output("%s %.*s", commit_hex_sha1(h2), msglen, msg);

	if ( ancestor )
		commit_list_insert(ancestor, &ca);
	else
		ca = get_merge_bases(h1, h2, 1);

	output("found %u common ancestor(s):", commit_list_count(ca));
	for (iter = ca; iter; iter = iter->next) {
		msg = commit_title(iter->item, &msglen);
		output("%s %.*s", commit_hex_sha1(iter->item), msglen, msg);
	}

	mergedCA = pop_commit(&ca);

	/* TODO: what happens when merge with virtual commits fails? */
	for (iter = ca; iter; iter = iter->next) {
		output_indent = callDepth + 1;
		result = merge(mergedCA, iter->item,
			       "Temporary merge branch 1",
			       "Temporary merge branch 2",
			       callDepth + 1,
			       NULL);
		mergedCA = result.commit;
		output_indent = callDepth;

		if ( !mergedCA )
			die("merge returned no commit");
	}

	if ( callDepth == 0 ) {
		setup_index(0);
		index_only = 0;
	} else {
		setup_index(1);
		git_read_tree(h1->tree);
		index_only = 1;
	}

	mtr = merge_trees(h1->tree, h2->tree,
			  mergedCA->tree, branch1Name, branch2Name);

	if ( !ancestor && (mtr.clean || index_only) ) {
		result.commit = make_virtual_commit(mtr.tree, "merged tree");
		commit_list_insert(h1, &result.commit->parents);
		commit_list_insert(h2, &result.commit->parents->next);
	} else
		result.commit = NULL;

	result.clean = mtr.clean;
	return result;
}

static struct commit *get_ref(const char *ref)
{
	unsigned char sha1[20];
	struct object *object;

	if (get_sha1(ref, sha1))
		die("Could not resolve ref '%s'", ref);
	object = deref_tag(parse_object(sha1), ref, strlen(ref));
	if (object->type != TYPE_COMMIT)
		return NULL;
	if (parse_commit((struct commit *)object))
		die("Could not parse commit '%s'", sha1_to_hex(object->sha1));
	return (struct commit *)object;
}

int main(int argc, char *argv[])
{
	static const char *bases[2];
	static unsigned bases_count = 0;

	original_index_file = getenv("GIT_INDEX_FILE");

	if (!original_index_file)
		original_index_file = strdup(git_path("index"));

	temporary_index_file = strdup(git_path("mrg-rcrsv-tmp-idx"));

	if (argc < 4)
		die("Usage: %s <base>... -- <head> <remote> ...\n", argv[0]);

	int i;
	for (i = 1; i < argc; ++i) {
		if (!strcmp(argv[i], "--"))
			break;
		if (bases_count < sizeof(bases)/sizeof(*bases))
			bases[bases_count++] = argv[i];
	}
	if (argc - i != 3) /* "--" "<head>" "<remote>" */
		die("Not handling anything other than two heads merge.");

	const char *branch1, *branch2;

	branch1 = argv[++i];
	branch2 = argv[++i];
	printf("Merging %s with %s\n", branch1, branch2);

	struct merge_result result;
	struct commit *h1 = get_ref(branch1);
	struct commit *h2 = get_ref(branch2);

	if (bases_count == 1) {
		struct commit *ancestor = get_ref(bases[0]);
		result = merge(h1, h2, branch1, branch2, 0, ancestor);
	} else
		result = merge(h1, h2, branch1, branch2, 0, NULL);

	if (cache_dirty)
		flush_cache();

	return result.clean ? 0: 1;
}

/*
vim: sw=8 noet
*/