fast-rebase: demonstrate merge-ort's API via new test-tool command
Add a new test-tool command named 'fast-rebase', which is a super-slimmed down and nowhere near as capable version of 'git rebase'. 'test-tool fast-rebase' is not currently planned for usage in the testsuite, but is here for two purposes: 1) Demonstrate the desired API of merge-ort. In particular, fast-rebase takes advantage of the separation of the merging operation from the updating of the index and working tree, to allow it to pick N commits, but only update the index and working tree once at the end. Look for the calls to merge_incore_nonrecursive() and merge_switch_to_result(). 2) Provide a convenient benchmark that isn't polluted by the heavy disk writing and forking of unnecessary processes that comes from sequencer.c and merge-recursive.c. fast-rebase is not meant to replace sequencer.c, just give ideas on how sequencer.c can be changed. Updating sequencer.c with these goals is probably a large amount of work; writing a simple targeted command with no documentation, less-than-useful help messages, numerous limitations in terms of flags it can accept and situations it can handle, and which is flagged off from users is a much easier interim step. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Elijah Newren committed
Oct 29, 2020 at 20:32 UTC
fe1a21d5267cae88d4312e3595909720717eb31c
4 files changed
+214
Makefile
+1
@@ -704,6 +704,7 @@ TEST_BUILTINS_OBJS += test-dump-fsmonitor.o
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TEST_BUILTINS_OBJS += test-dump-split-index.o
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TEST_BUILTINS_OBJS += test-dump-untracked-cache.o
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TEST_BUILTINS_OBJS += test-example-decorate.o
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+TEST_BUILTINS_OBJS += test-fast-rebase.o
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TEST_BUILTINS_OBJS += test-genrandom.o
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TEST_BUILTINS_OBJS += test-genzeros.o
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TEST_BUILTINS_OBJS += test-hash-speed.o
t/helper/test-fast-rebase.c
new
+211
@@ -0,0 +1,211 @@
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+/*
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+ * "git fast-rebase" builtin command
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+ *
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+ * FAST: Forking Any Subprocesses (is) Taboo
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+ *
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+ * This is meant SOLELY as a demo of what is possible. sequencer.c and
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+ * rebase.c should be refactored to use the ideas here, rather than attempting
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+ * to extend this file to replace those (unless Phillip or Dscho say that
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+ * refactoring is too hard and we need a clean slate, but I'm guessing that
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+ * refactoring is the better route).
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+ */
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+
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+#define USE_THE_INDEX_COMPATIBILITY_MACROS
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+#include "test-tool.h"
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+
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+#include "cache-tree.h"
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+#include "commit.h"
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+#include "lockfile.h"
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+#include "merge-ort.h"
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+#include "refs.h"
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+#include "revision.h"
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+#include "sequencer.h"
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+#include "strvec.h"
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+#include "tree.h"
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+
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+static const char *short_commit_name(struct commit *commit)
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+{
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+ return find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV);
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+}
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+
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+static struct commit *peel_committish(const char *name)
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+{
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+ struct object *obj;
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+ struct object_id oid;
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+
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+ if (get_oid(name, &oid))
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+ return NULL;
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+ obj = parse_object(the_repository, &oid);
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+ return (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);
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+}
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+
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+static char *get_author(const char *message)
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+{
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+ size_t len;
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+ const char *a;
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+
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+ a = find_commit_header(message, "author", &len);
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+ if (a)
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+ return xmemdupz(a, len);
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+
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+ return NULL;
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+}
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+
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+static struct commit *create_commit(struct tree *tree,
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+ struct commit *based_on,
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+ struct commit *parent)
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+{
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+ struct object_id ret;
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+ struct object *obj;
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+ struct commit_list *parents = NULL;
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+ char *author;
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+ char *sign_commit = NULL;
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+ struct commit_extra_header *extra;
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+ struct strbuf msg = STRBUF_INIT;
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+ const char *out_enc = get_commit_output_encoding();
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+ const char *message = logmsg_reencode(based_on, NULL, out_enc);
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+ const char *orig_message = NULL;
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+ const char *exclude_gpgsig[] = { "gpgsig", NULL };
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+
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+ commit_list_insert(parent, &parents);
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+ extra = read_commit_extra_headers(based_on, exclude_gpgsig);
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+ find_commit_subject(message, &orig_message);
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+ strbuf_addstr(&msg, orig_message);
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+ author = get_author(message);
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+ reset_ident_date();
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+ if (commit_tree_extended(msg.buf, msg.len, &tree->object.oid, parents,
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+ &ret, author, NULL, sign_commit, extra)) {
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+ error(_("failed to write commit object"));
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+ return NULL;
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+ }
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+ free(author);
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+ strbuf_release(&msg);
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+
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+ obj = parse_object(the_repository, &ret);
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+ return (struct commit *)obj;
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+}
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+
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+int cmd__fast_rebase(int argc, const char **argv)
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+{
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+ struct commit *onto;
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+ struct commit *last_commit = NULL, *last_picked_commit = NULL;
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+ struct object_id head;
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+ struct lock_file lock = LOCK_INIT;
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+ int clean = 1;
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+ struct strvec rev_walk_args = STRVEC_INIT;
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+ struct rev_info revs;
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+ struct commit *commit;
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+ struct merge_options merge_opt;
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+ struct tree *next_tree, *base_tree, *head_tree;
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+ struct merge_result result;
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+ struct strbuf reflog_msg = STRBUF_INIT;
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+ struct strbuf branch_name = STRBUF_INIT;
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+
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+ /*
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+ * test-tool stuff doesn't set up the git directory by default; need to
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+ * do that manually.
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+ */
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+ setup_git_directory();
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+
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+ if (argc == 2 && !strcmp(argv[1], "-h")) {
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+ printf("Sorry, I am not a psychiatrist; I can not give you the help you need. Oh, you meant usage...\n");
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+ exit(129);
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+ }
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+
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+ if (argc != 5 || strcmp(argv[1], "--onto"))
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+ die("usage: read the code, figure out how to use it, then do so");
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+
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+ onto = peel_committish(argv[2]);
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+ strbuf_addf(&branch_name, "refs/heads/%s", argv[4]);
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+
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+ /* Sanity check */
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+ if (get_oid("HEAD", &head))
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+ die(_("Cannot read HEAD"));
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+ assert(oideq(&onto->object.oid, &head));
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+
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+ hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
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+ assert(repo_read_index(the_repository) >= 0);
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+
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+ repo_init_revisions(the_repository, &revs, NULL);
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+ revs.verbose_header = 1;
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+ revs.max_parents = 1;
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+ revs.cherry_mark = 1;
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+ revs.limited = 1;
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+ revs.reverse = 1;
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+ revs.right_only = 1;
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+ revs.sort_order = REV_SORT_IN_GRAPH_ORDER;
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+ revs.topo_order = 1;
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+ strvec_pushl(&rev_walk_args, "", argv[4], "--not", argv[3], NULL);
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+
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+ if (setup_revisions(rev_walk_args.nr, rev_walk_args.v, &revs, NULL) > 1)
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+ return error(_("unhandled options"));
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+
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+ strvec_clear(&rev_walk_args);
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+
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+ if (prepare_revision_walk(&revs) < 0)
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+ return error(_("error preparing revisions"));
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+
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+ init_merge_options(&merge_opt, the_repository);
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+ memset(&result, 0, sizeof(result));
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+ merge_opt.show_rename_progress = 1;
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+ merge_opt.branch1 = "HEAD";
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+ head_tree = get_commit_tree(onto);
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+ result.tree = head_tree;
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+ last_commit = onto;
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+ while ((commit = get_revision(&revs))) {
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+ struct commit *base;
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+
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+ fprintf(stderr, "Rebasing %s...\r",
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+ oid_to_hex(&commit->object.oid));
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+ assert(commit->parents && !commit->parents->next);
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+ base = commit->parents->item;
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+
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+ next_tree = get_commit_tree(commit);
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+ base_tree = get_commit_tree(base);
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+
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+ merge_opt.branch2 = short_commit_name(commit);
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+ merge_opt.ancestor = xstrfmt("parent of %s", merge_opt.branch2);
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+
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+ merge_incore_nonrecursive(&merge_opt,
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+ base_tree,
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+ result.tree,
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+ next_tree,
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+ &result);
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+
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+ free((char*)merge_opt.ancestor);
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+ merge_opt.ancestor = NULL;
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+ if (!result.clean)
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+ die("Aborting: Hit a conflict and restarting is not implemented.");
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+ last_picked_commit = commit;
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+ last_commit = create_commit(result.tree, commit, last_commit);
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+ }
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+ fprintf(stderr, "\nDone.\n");
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+ /* TODO: There should be some kind of rev_info_free(&revs) call... */
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+ memset(&revs, 0, sizeof(revs));
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+
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+ merge_switch_to_result(&merge_opt, head_tree, &result, 1, !result.clean);
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+
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+ if (result.clean < 0)
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+ exit(128);
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+
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+ strbuf_addf(&reflog_msg, "finish rebase %s onto %s",
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+ oid_to_hex(&last_picked_commit->object.oid),
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+ oid_to_hex(&last_commit->object.oid));
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+ if (update_ref(reflog_msg.buf, branch_name.buf,
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+ &last_commit->object.oid,
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+ &last_picked_commit->object.oid,
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+ REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR)) {
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+ error(_("could not update %s"), argv[4]);
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+ die("Failed to update %s", argv[4]);
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+ }
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+ if (create_symref("HEAD", branch_name.buf, reflog_msg.buf) < 0)
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+ die(_("unable to update HEAD"));
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+ strbuf_release(&reflog_msg);
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+ strbuf_release(&branch_name);
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+
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+ prime_cache_tree(the_repository, the_repository->index, result.tree);
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+ if (write_locked_index(&the_index, &lock,
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+ COMMIT_LOCK | SKIP_IF_UNCHANGED))
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+ die(_("unable to write %s"), get_index_file());
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+ return (clean == 0);
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+}
t/helper/test-tool.c
+1
@@ -28,6 +28,7 @@ static struct test_cmd cmds[] = {
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{ "dump-split-index", cmd__dump_split_index },
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{ "dump-untracked-cache", cmd__dump_untracked_cache },
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{ "example-decorate", cmd__example_decorate },
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+ { "fast-rebase", cmd__fast_rebase },
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{ "genrandom", cmd__genrandom },
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{ "genzeros", cmd__genzeros },
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{ "hashmap", cmd__hashmap },
t/helper/test-tool.h
+1
@@ -18,6 +18,7 @@ int cmd__dump_fsmonitor(int argc, const char **argv);
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int cmd__dump_split_index(int argc, const char **argv);
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int cmd__dump_untracked_cache(int argc, const char **argv);
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int cmd__example_decorate(int argc, const char **argv);
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+int cmd__fast_rebase(int argc, const char **argv);
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int cmd__genrandom(int argc, const char **argv);
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int cmd__genzeros(int argc, const char **argv);
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int cmd__hashmap(int argc, const char **argv);