git/builtin/merge-tree.c
Elijah Newren 7976721d17 merge-tree: add a --allow-unrelated-histories flag
Folks may want to merge histories that have no common ancestry; provide
a flag with the same name as used by `git merge` to allow this.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-06-22 16:10:06 -07:00

552 lines
14 KiB
C

#define USE_THE_INDEX_COMPATIBILITY_MACROS
#include "builtin.h"
#include "tree-walk.h"
#include "xdiff-interface.h"
#include "help.h"
#include "commit-reach.h"
#include "merge-ort.h"
#include "object-store.h"
#include "parse-options.h"
#include "repository.h"
#include "blob.h"
#include "exec-cmd.h"
#include "merge-blobs.h"
#include "quote.h"
static int line_termination = '\n';
struct merge_list {
struct merge_list *next;
struct merge_list *link; /* other stages for this object */
unsigned int stage : 2;
unsigned int mode;
const char *path;
struct blob *blob;
};
static struct merge_list *merge_result, **merge_result_end = &merge_result;
static void add_merge_entry(struct merge_list *entry)
{
*merge_result_end = entry;
merge_result_end = &entry->next;
}
static void trivial_merge_trees(struct tree_desc t[3], const char *base);
static const char *explanation(struct merge_list *entry)
{
switch (entry->stage) {
case 0:
return "merged";
case 3:
return "added in remote";
case 2:
if (entry->link)
return "added in both";
return "added in local";
}
/* Existed in base */
entry = entry->link;
if (!entry)
return "removed in both";
if (entry->link)
return "changed in both";
if (entry->stage == 3)
return "removed in local";
return "removed in remote";
}
static void *result(struct merge_list *entry, unsigned long *size)
{
enum object_type type;
struct blob *base, *our, *their;
const char *path = entry->path;
if (!entry->stage)
return read_object_file(&entry->blob->object.oid, &type, size);
base = NULL;
if (entry->stage == 1) {
base = entry->blob;
entry = entry->link;
}
our = NULL;
if (entry && entry->stage == 2) {
our = entry->blob;
entry = entry->link;
}
their = NULL;
if (entry)
their = entry->blob;
return merge_blobs(the_repository->index, path,
base, our, their, size);
}
static void *origin(struct merge_list *entry, unsigned long *size)
{
enum object_type type;
while (entry) {
if (entry->stage == 2)
return read_object_file(&entry->blob->object.oid,
&type, size);
entry = entry->link;
}
return NULL;
}
static int show_outf(void *priv_, mmbuffer_t *mb, int nbuf)
{
int i;
for (i = 0; i < nbuf; i++)
printf("%.*s", (int) mb[i].size, mb[i].ptr);
return 0;
}
static void show_diff(struct merge_list *entry)
{
unsigned long size;
mmfile_t src, dst;
xpparam_t xpp;
xdemitconf_t xecfg;
xdemitcb_t ecb = { .out_line = show_outf };
memset(&xpp, 0, sizeof(xpp));
xpp.flags = 0;
memset(&xecfg, 0, sizeof(xecfg));
xecfg.ctxlen = 3;
src.ptr = origin(entry, &size);
if (!src.ptr)
size = 0;
src.size = size;
dst.ptr = result(entry, &size);
if (!dst.ptr)
size = 0;
dst.size = size;
if (xdi_diff(&src, &dst, &xpp, &xecfg, &ecb))
die("unable to generate diff");
free(src.ptr);
free(dst.ptr);
}
static void show_result_list(struct merge_list *entry)
{
printf("%s\n", explanation(entry));
do {
struct merge_list *link = entry->link;
static const char *desc[4] = { "result", "base", "our", "their" };
printf(" %-6s %o %s %s\n", desc[entry->stage], entry->mode, oid_to_hex(&entry->blob->object.oid), entry->path);
entry = link;
} while (entry);
}
static void show_result(void)
{
struct merge_list *walk;
walk = merge_result;
while (walk) {
show_result_list(walk);
show_diff(walk);
walk = walk->next;
}
}
/* 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 !is_null_oid(&a->oid) &&
!is_null_oid(&b->oid) &&
oideq(&a->oid, &b->oid) &&
a->mode == b->mode;
}
static int both_empty(struct name_entry *a, struct name_entry *b)
{
return is_null_oid(&a->oid) && is_null_oid(&b->oid);
}
static struct merge_list *create_entry(unsigned stage, unsigned mode, const struct object_id *oid, const char *path)
{
struct merge_list *res = xcalloc(1, sizeof(*res));
res->stage = stage;
res->path = path;
res->mode = mode;
res->blob = lookup_blob(the_repository, oid);
return res;
}
static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
{
struct strbuf buf = STRBUF_INIT;
strbuf_make_traverse_path(&buf, info, n->path, n->pathlen);
return strbuf_detach(&buf, NULL);
}
static void resolve(const struct traverse_info *info, struct name_entry *ours, struct name_entry *result)
{
struct merge_list *orig, *final;
const char *path;
/* If it's already ours, don't bother showing it */
if (!ours)
return;
path = traverse_path(info, result);
orig = create_entry(2, ours->mode, &ours->oid, path);
final = create_entry(0, result->mode, &result->oid, path);
final->link = orig;
add_merge_entry(final);
}
static void unresolved_directory(const struct traverse_info *info,
struct name_entry n[3])
{
struct repository *r = the_repository;
char *newbase;
struct name_entry *p;
struct tree_desc t[3];
void *buf0, *buf1, *buf2;
for (p = n; p < n + 3; p++) {
if (p->mode && S_ISDIR(p->mode))
break;
}
if (n + 3 <= p)
return; /* there is no tree here */
newbase = traverse_path(info, p);
#define ENTRY_OID(e) (((e)->mode && S_ISDIR((e)->mode)) ? &(e)->oid : NULL)
buf0 = fill_tree_descriptor(r, t + 0, ENTRY_OID(n + 0));
buf1 = fill_tree_descriptor(r, t + 1, ENTRY_OID(n + 1));
buf2 = fill_tree_descriptor(r, t + 2, ENTRY_OID(n + 2));
#undef ENTRY_OID
trivial_merge_trees(t, newbase);
free(buf0);
free(buf1);
free(buf2);
free(newbase);
}
static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
{
const char *path;
struct merge_list *link;
if (!n->mode)
return entry;
if (entry)
path = entry->path;
else
path = traverse_path(info, n);
link = create_entry(stage, n->mode, &n->oid, path);
link->link = entry;
return link;
}
static void unresolved(const struct traverse_info *info, struct name_entry n[3])
{
struct merge_list *entry = NULL;
int i;
unsigned dirmask = 0, mask = 0;
for (i = 0; i < 3; i++) {
mask |= (1 << i);
/*
* Treat missing entries as directories so that we return
* after unresolved_directory has handled this.
*/
if (!n[i].mode || S_ISDIR(n[i].mode))
dirmask |= (1 << i);
}
unresolved_directory(info, n);
if (dirmask == mask)
return;
if (n[2].mode && !S_ISDIR(n[2].mode))
entry = link_entry(3, info, n + 2, entry);
if (n[1].mode && !S_ISDIR(n[1].mode))
entry = link_entry(2, info, n + 1, entry);
if (n[0].mode && !S_ISDIR(n[0].mode))
entry = link_entry(1, info, n + 0, entry);
add_merge_entry(entry);
}
/*
* 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 int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
{
/* Same in both? */
if (same_entry(entry+1, entry+2) || both_empty(entry+1, entry+2)) {
/* Modified, added or removed identically */
resolve(info, NULL, entry+1);
return mask;
}
if (same_entry(entry+0, entry+1)) {
if (!is_null_oid(&entry[2].oid) && !S_ISDIR(entry[2].mode)) {
/* We did not touch, they modified -- take theirs */
resolve(info, entry+1, entry+2);
return mask;
}
/*
* If we did not touch a directory but they made it
* into a file, we fall through and unresolved()
* recurses down. Likewise for the opposite case.
*/
}
if (same_entry(entry+0, entry+2) || both_empty(entry+0, entry+2)) {
/* We added, modified or removed, they did not touch -- take ours */
resolve(info, NULL, entry+1);
return mask;
}
unresolved(info, entry);
return mask;
}
static void trivial_merge_trees(struct tree_desc t[3], const char *base)
{
struct traverse_info info;
setup_traverse_info(&info, base);
info.fn = threeway_callback;
traverse_trees(&the_index, 3, t, &info);
}
static void *get_tree_descriptor(struct repository *r,
struct tree_desc *desc,
const char *rev)
{
struct object_id oid;
void *buf;
if (repo_get_oid(r, rev, &oid))
die("unknown rev %s", rev);
buf = fill_tree_descriptor(r, desc, &oid);
if (!buf)
die("%s is not a tree", rev);
return buf;
}
static int trivial_merge(const char *base,
const char *branch1,
const char *branch2)
{
struct repository *r = the_repository;
struct tree_desc t[3];
void *buf1, *buf2, *buf3;
buf1 = get_tree_descriptor(r, t+0, base);
buf2 = get_tree_descriptor(r, t+1, branch1);
buf3 = get_tree_descriptor(r, t+2, branch2);
trivial_merge_trees(t, "");
free(buf1);
free(buf2);
free(buf3);
show_result();
return 0;
}
enum mode {
MODE_UNKNOWN,
MODE_TRIVIAL,
MODE_REAL,
};
struct merge_tree_options {
int mode;
int allow_unrelated_histories;
int show_messages;
int name_only;
};
static int real_merge(struct merge_tree_options *o,
const char *branch1, const char *branch2,
const char *prefix)
{
struct commit *parent1, *parent2;
struct commit_list *merge_bases = NULL;
struct merge_options opt;
struct merge_result result = { 0 };
parent1 = get_merge_parent(branch1);
if (!parent1)
help_unknown_ref(branch1, "merge-tree",
_("not something we can merge"));
parent2 = get_merge_parent(branch2);
if (!parent2)
help_unknown_ref(branch2, "merge-tree",
_("not something we can merge"));
init_merge_options(&opt, the_repository);
opt.show_rename_progress = 0;
opt.branch1 = branch1;
opt.branch2 = branch2;
/*
* Get the merge bases, in reverse order; see comment above
* merge_incore_recursive in merge-ort.h
*/
merge_bases = get_merge_bases(parent1, parent2);
if (!merge_bases && !o->allow_unrelated_histories)
die(_("refusing to merge unrelated histories"));
merge_bases = reverse_commit_list(merge_bases);
merge_incore_recursive(&opt, merge_bases, parent1, parent2, &result);
if (result.clean < 0)
die(_("failure to merge"));
if (o->show_messages == -1)
o->show_messages = !result.clean;
printf("%s%c", oid_to_hex(&result.tree->object.oid), line_termination);
if (!result.clean) {
struct string_list conflicted_files = STRING_LIST_INIT_NODUP;
const char *last = NULL;
int i;
merge_get_conflicted_files(&result, &conflicted_files);
for (i = 0; i < conflicted_files.nr; i++) {
const char *name = conflicted_files.items[i].string;
struct stage_info *c = conflicted_files.items[i].util;
if (!o->name_only)
printf("%06o %s %d\t",
c->mode, oid_to_hex(&c->oid), c->stage);
else if (last && !strcmp(last, name))
continue;
write_name_quoted_relative(
name, prefix, stdout, line_termination);
last = name;
}
string_list_clear(&conflicted_files, 1);
}
if (o->show_messages) {
putchar(line_termination);
merge_display_update_messages(&opt, line_termination == '\0',
&result);
}
merge_finalize(&opt, &result);
return !result.clean; /* result.clean < 0 handled above */
}
int cmd_merge_tree(int argc, const char **argv, const char *prefix)
{
struct merge_tree_options o = { .show_messages = -1 };
int expected_remaining_argc;
int original_argc;
const char * const merge_tree_usage[] = {
N_("git merge-tree [--write-tree] [<options>] <branch1> <branch2>"),
N_("git merge-tree [--trivial-merge] <base-tree> <branch1> <branch2>"),
NULL
};
struct option mt_options[] = {
OPT_CMDMODE(0, "write-tree", &o.mode,
N_("do a real merge instead of a trivial merge"),
MODE_REAL),
OPT_CMDMODE(0, "trivial-merge", &o.mode,
N_("do a trivial merge only"), MODE_TRIVIAL),
OPT_BOOL(0, "messages", &o.show_messages,
N_("also show informational/conflict messages")),
OPT_SET_INT('z', NULL, &line_termination,
N_("separate paths with the NUL character"), '\0'),
OPT_BOOL_F(0, "name-only",
&o.name_only,
N_("list filenames without modes/oids/stages"),
PARSE_OPT_NONEG),
OPT_BOOL_F(0, "allow-unrelated-histories",
&o.allow_unrelated_histories,
N_("allow merging unrelated histories"),
PARSE_OPT_NONEG),
OPT_END()
};
/* Parse arguments */
original_argc = argc - 1; /* ignoring argv[0] */
argc = parse_options(argc, argv, prefix, mt_options,
merge_tree_usage, PARSE_OPT_STOP_AT_NON_OPTION);
switch (o.mode) {
default:
BUG("unexpected command mode %d", o.mode);
case MODE_UNKNOWN:
switch (argc) {
default:
usage_with_options(merge_tree_usage, mt_options);
case 2:
o.mode = MODE_REAL;
break;
case 3:
o.mode = MODE_TRIVIAL;
break;
}
expected_remaining_argc = argc;
break;
case MODE_REAL:
expected_remaining_argc = 2;
break;
case MODE_TRIVIAL:
expected_remaining_argc = 3;
/* Removal of `--trivial-merge` is expected */
original_argc--;
break;
}
if (o.mode == MODE_TRIVIAL && argc < original_argc)
die(_("--trivial-merge is incompatible with all other options"));
if (argc != expected_remaining_argc)
usage_with_options(merge_tree_usage, mt_options);
/* Do the relevant type of merge */
if (o.mode == MODE_REAL)
return real_merge(&o, argv[0], argv[1], prefix);
else
return trivial_merge(argv[0], argv[1], argv[2]);
}