diff options
Diffstat (limited to 'merge-tree.c')
| -rw-r--r-- | merge-tree.c | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/merge-tree.c b/merge-tree.c new file mode 100644 index 0000000000..0d6d43403b --- /dev/null +++ b/merge-tree.c @@ -0,0 +1,238 @@ +#include "cache.h" +#include "diff.h" + +static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>"; +static int resolve_directories = 1; + +static void merge_trees(struct tree_desc t[3], const char *base); + +static void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1) +{ + unsigned long size = 0; + void *buf = NULL; + + if (sha1) { + buf = read_object_with_reference(sha1, "tree", &size, NULL); + if (!buf) + die("unable to read tree %s", sha1_to_hex(sha1)); + } + desc->size = size; + desc->buf = buf; + return buf; +} + +struct name_entry { + const unsigned char *sha1; + const char *path; + unsigned int mode; + int pathlen; +}; + +static void entry_clear(struct name_entry *a) +{ + memset(a, 0, sizeof(*a)); +} + +static int entry_compare(struct name_entry *a, struct name_entry *b) +{ + return base_name_compare( + a->path, a->pathlen, a->mode, + b->path, b->pathlen, b->mode); +} + +static void entry_extract(struct tree_desc *t, struct name_entry *a) +{ + a->sha1 = tree_entry_extract(t, &a->path, &a->mode); + a->pathlen = strlen(a->path); +} + +/* An empty entry never compares same, not even to another empty entry */ +static int same_entry(struct name_entry *a, struct name_entry *b) +{ + return a->sha1 && + b->sha1 && + !memcmp(a->sha1, b->sha1, 20) && + a->mode == b->mode; +} + +static void resolve(const char *base, struct name_entry *result) +{ + printf("0 %06o %s %s%s\n", result->mode, sha1_to_hex(result->sha1), base, result->path); +} + +static int unresolved_directory(const char *base, struct name_entry n[3]) +{ + int baselen; + char *newbase; + struct name_entry *p; + struct tree_desc t[3]; + void *buf0, *buf1, *buf2; + + if (!resolve_directories) + return 0; + p = n; + if (!p->mode) { + p++; + if (!p->mode) + p++; + } + if (!S_ISDIR(p->mode)) + return 0; + baselen = strlen(base); + newbase = xmalloc(baselen + p->pathlen + 2); + memcpy(newbase, base, baselen); + memcpy(newbase + baselen, p->path, p->pathlen); + memcpy(newbase + baselen + p->pathlen, "/", 2); + + buf0 = fill_tree_descriptor(t+0, n[0].sha1); + buf1 = fill_tree_descriptor(t+1, n[1].sha1); + buf2 = fill_tree_descriptor(t+2, n[2].sha1); + merge_trees(t, newbase); + + free(buf0); + free(buf1); + free(buf2); + free(newbase); + return 1; +} + +static void unresolved(const char *base, struct name_entry n[3]) +{ + if (unresolved_directory(base, n)) + return; + printf("1 %06o %s %s%s\n", n[0].mode, sha1_to_hex(n[0].sha1), base, n[0].path); + printf("2 %06o %s %s%s\n", n[1].mode, sha1_to_hex(n[1].sha1), base, n[1].path); + printf("3 %06o %s %s%s\n", n[2].mode, sha1_to_hex(n[2].sha1), base, n[2].path); +} + +/* + * Merge two trees together (t[1] and t[2]), using a common base (t[0]) + * as the origin. + * + * This walks the (sorted) trees in lock-step, checking every possible + * name. Note that directories automatically sort differently from other + * files (see "base_name_compare"), so you'll never see file/directory + * conflicts, because they won't ever compare the same. + * + * IOW, if a directory changes to a filename, it will automatically be + * seen as the directory going away, and the filename being created. + * + * Think of this as a three-way diff. + * + * The output will be either: + * - successful merge + * "0 mode sha1 filename" + * NOTE NOTE NOTE! FIXME! We really really need to walk the index + * in parallel with this too! + * + * - conflict: + * "1 mode sha1 filename" + * "2 mode sha1 filename" + * "3 mode sha1 filename" + * where not all of the 1/2/3 lines may exist, of course. + * + * The successful merge rules are the same as for the three-way merge + * in git-read-tree. + */ +static void merge_trees(struct tree_desc t[3], const char *base) +{ + for (;;) { + struct name_entry entry[3]; + unsigned int mask = 0; + int i, last; + + last = -1; + for (i = 0; i < 3; i++) { + if (!t[i].size) + continue; + entry_extract(t+i, entry+i); + if (last >= 0) { + int cmp = entry_compare(entry+i, entry+last); + + /* + * Is the new name bigger than the old one? + * Ignore it + */ + if (cmp > 0) + continue; + /* + * Is the new name smaller than the old one? + * Ignore all old ones + */ + if (cmp < 0) + mask = 0; + } + mask |= 1u << i; + last = i; + } + if (!mask) + break; + + /* + * Update the tree entries we've walked, and clear + * all the unused name-entries. + */ + for (i = 0; i < 3; i++) { + if (mask & (1u << i)) { + update_tree_entry(t+i); + continue; + } + entry_clear(entry + i); + } + + /* Same in both? */ + if (same_entry(entry+1, entry+2)) { + if (entry[0].sha1) { + resolve(base, entry+1); + continue; + } + } + + if (same_entry(entry+0, entry+1)) { + if (entry[2].sha1) { + resolve(base, entry+2); + continue; + } + } + + if (same_entry(entry+0, entry+2)) { + if (entry[1].sha1) { + resolve(base, entry+1); + continue; + } + } + + unresolved(base, entry); + } +} + +static void *get_tree_descriptor(struct tree_desc *desc, const char *rev) +{ + unsigned char sha1[20]; + void *buf; + + if (get_sha1(rev, sha1) < 0) + die("unknown rev %s", rev); + buf = fill_tree_descriptor(desc, sha1); + if (!buf) + die("%s is not a tree", rev); + return buf; +} + +int main(int argc, char **argv) +{ + struct tree_desc t[3]; + void *buf1, *buf2, *buf3; + + if (argc < 4) + usage(merge_tree_usage); + + buf1 = get_tree_descriptor(t+0, argv[1]); + buf2 = get_tree_descriptor(t+1, argv[2]); + buf3 = get_tree_descriptor(t+2, argv[3]); + merge_trees(t, ""); + free(buf1); + free(buf2); + free(buf3); + return 0; +} |