From: Stefan Xenos <sxe...@google.com>
metacommit.c supports the creation of metacommits and
adds the API needed to create and update changes.
Create the "modify_change" function that can be called from modification
commands like "rebase" and "git amend" to record obsolescences in the
change graph.
Create the "record_metacommit" function for recording more complicated
commit relationships in the commit graph.
Create the "write_metacommit" function for low-level creation of
metacommits.
---
Makefile | 1 +
metacommit.c | 370 +++++++++++++++++++++++++++++++++++++++++++++++++++
metacommit.h | 39 ++++++
3 files changed, 410 insertions(+)
create mode 100644 metacommit.c
create mode 100644 metacommit.h
diff --git a/Makefile b/Makefile
index 09cfd3ef1b..a6be1780c5 100644
--- a/Makefile
+++ b/Makefile
@@ -920,6 +920,7 @@ LIB_OBJS += merge.o
LIB_OBJS += merge-blobs.o
LIB_OBJS += merge-recursive.o
LIB_OBJS += mergesort.o
+LIB_OBJS += metacommit.o
LIB_OBJS += metacommit-parser.o
LIB_OBJS += midx.o
LIB_OBJS += name-hash.o
diff --git a/metacommit.c b/metacommit.c
new file mode 100644
index 0000000000..705e54f3aa
--- /dev/null
+++ b/metacommit.c
@@ -0,0 +1,370 @@
+#include "cache.h"
+#include "metacommit.h"
+#include "commit.h"
+#include "change-table.h"
+#include "refs.h"
+
+void init_metacommit_data(struct metacommit_data *state)
+{
+ memset(state, 0, sizeof(*state));
+}
+
+void clear_metacommit_data(struct metacommit_data *state)
+{
+ oid_array_clear(&state->replace);
+ oid_array_clear(&state->origin);
+}
+
+static void compute_default_change_name(struct commit *initial_commit,
+ struct strbuf* result)
+{
+ const char *buffer = get_commit_buffer(initial_commit, NULL);
+ const char *subject;
+ const char *eol;
+ int len;
+ find_commit_subject(buffer, &subject);
+ eol = strchrnul(subject, '\n');
+ for (len = 0;subject < eol && len < 10; ++subject, ++len) {
+ char next = *subject;
+ if (isspace(next)) {
+ continue;
+ }
+
+ strbuf_addch(result, next);
+ }
+}
+
+/*
+ * Computes a change name for a change rooted at the given initial commit. Good
+ * change names should be memorable, unique, and easy to type. They are not
+ * required to match the commit comment.
+ */
+static void compute_change_name(struct commit *initial_commit, struct strbuf*
result)
+{
+ struct strbuf default_name;
+ struct object_id unused;
+
+ strbuf_init(&default_name, 0);
+ if (initial_commit) {
+ compute_default_change_name(initial_commit, &default_name);
+ } else {
+ strbuf_addstr(&default_name, "change");
+ }
+ strbuf_addstr(result, "refs/metas/");
+ strbuf_addstr(result, default_name.buf);
+
+ // If there is already a change of this name, append a suffix
+ if (!read_ref(result->buf, &unused)) {
+ int suffix = 2;
+ int original_length = result->len;
+
+ while (1) {
+ strbuf_addf(result, "%d", suffix);
+ if (read_ref(result->buf, &unused)) {
+ break;
+ }
+ strbuf_remove(result, original_length, result->len -
original_length);
+ ++suffix;
+ }
+ }
+
+ strbuf_release(&default_name);
+}
+
+struct resolve_metacommit_callback_data
+{
+ struct change_table* active_changes;
+ struct string_list *changes;
+ struct oid_array *heads;
+};
+
+static int resolve_metacommit_callback(const char *refname, void *cb_data)
+{
+ struct resolve_metacommit_callback_data *data = (struct
resolve_metacommit_callback_data *)cb_data;
+ struct change_head *chhead;
+
+ chhead = get_change_head(data->active_changes, refname);
+
+ if (data->changes) {
+ string_list_append(data->changes, refname)->util =
&(chhead->head);
+ }
+ if (data->heads) {
+ oid_array_append(data->heads, &(chhead->head));
+ }
+
+ return 0;
+}
+
+/*
+ * Produces the final form of a metacommit based on the current change refs.
+ */
+static void resolve_metacommit(
+ struct repository* repo,
+ struct change_table* active_changes,
+ const struct metacommit_data *to_resolve,
+ struct metacommit_data *resolved_output,
+ struct string_list *to_advance,
+ int allow_append)
+{
+ int i;
+ int len = to_resolve->replace.nr;
+ struct resolve_metacommit_callback_data cbdata;
+ int old_change_list_length = to_advance->nr;
+ struct commit* content;
+
+ oidcpy(&resolved_output->content, &to_resolve->content);
+
+ // First look for changes that point to any of the replacement edges in
the
+ // metacommit. These will be the changes that get advanced by this
metacommit.
+ resolved_output->abandoned = to_resolve->abandoned;
+ cbdata.active_changes = active_changes;
+ cbdata.changes = to_advance;
+ cbdata.heads = &(resolved_output->replace);
+
+ if (allow_append) {
+ for (i = 0; i < len; i++) {
+ int old_number = resolved_output->replace.nr;
+ for_each_change_referencing(active_changes,
&(to_resolve->replace.oid[i]),
+ resolve_metacommit_callback, &cbdata);
+ // If no changes were found, use the unresolved value
+ if (old_number == resolved_output->replace.nr) {
+ oid_array_append(&(resolved_output->replace),
&(to_resolve->replace.oid[i]));
+ }
+ }
+ }
+
+ cbdata.changes = NULL;
+ cbdata.heads = &(resolved_output->origin);
+
+ len = to_resolve->origin.nr;
+ for (i = 0; i < len; i++) {
+ int old_number = resolved_output->origin.nr;
+ for_each_change_referencing(active_changes,
&(to_resolve->origin.oid[i]),
+ resolve_metacommit_callback, &cbdata);
+ if (old_number == resolved_output->origin.nr) {
+ oid_array_append(&(resolved_output->origin),
&(to_resolve->origin.oid[i]));
+ }
+ }
+
+ // If no changes were advanced by this metacommit, we'll need to create
a new
+ // one.
+ if (to_advance->nr == old_change_list_length) {
+ struct strbuf change_name;
+
+ strbuf_init(&change_name, 80);
+ content = lookup_commit_reference_gently(repo,
&(to_resolve->content), 1);
+
+ compute_change_name(content, &change_name);
+ string_list_append(to_advance, change_name.buf);
+ strbuf_release(&change_name);
+ }
+}
+
+static void lookup_commits(
+ struct repository *repo,
+ struct oid_array *to_lookup,
+ struct commit_list **result)
+{
+ int i = to_lookup->nr;
+
+ while (--i >= 0) {
+ struct object_id *next = &(to_lookup->oid[i]);
+ struct commit *commit = lookup_commit_reference_gently(repo,
next, 1);
+ commit_list_insert(commit, result);
+ }
+}
+
+#define PARENT_TYPE_PREFIX "parent-type "
+
+/*
+ * Creates a new metacommit object with the given content. Writes the object
+ * id of the newly-created commit to result.
+ */
+int write_metacommit(struct repository *repo, struct metacommit_data *state,
+ struct object_id *result)
+{
+ struct commit_list *parents = NULL;
+ struct strbuf comment;
+ int i;
+ struct commit *content;
+
+ strbuf_init(&comment, strlen(PARENT_TYPE_PREFIX)
+ + 1 + 2 * (state->origin.nr + state->replace.nr));
+ lookup_commits(repo, &state->origin, &parents);
+ lookup_commits(repo, &state->replace, &parents);
+ content = lookup_commit_reference_gently(repo, &state->content, 1);
+ if (!content) {
+ strbuf_release(&comment);
+ free_commit_list(parents);
+ return -1;
+ }
+ commit_list_insert(content, &parents);
+
+ strbuf_addstr(&comment, PARENT_TYPE_PREFIX);
+ strbuf_addstr(&comment, state->abandoned ? "a" : "c");
+ for (i = 0; i < state->replace.nr; i++) {
+ strbuf_addstr(&comment, " r");
+ }
+
+ for (i = 0; i < state->origin.nr; i++) {
+ strbuf_addstr(&comment, " o");
+ }
+
+ // The parents list will be freed by this call
+ commit_tree(comment.buf, comment.len, repo->hash_algo->empty_tree,
parents,
+ result, NULL, NULL);
+
+ strbuf_release(&comment);
+ return 0;
+}
+
+/*
+ * Returns true iff the given metacommit is abandoned, has one or more origin
+ * parents, or has one or more replacement parents.
+ */
+static int is_nontrivial_metacommit(struct metacommit_data *state)
+{
+ return state->replace.nr || state->origin.nr || state->abandoned;
+}
+
+/*
+ * Records the relationships described by the given metacommit in the
+ * repository.
+ *
+ * If override_change is NULL (the default), an attempt will be made
+ * to append to existing changes wherever possible instead of creating new
ones.
+ * If override_change is non-null, only the given change ref will be updated.
+ *
+ * options is a bitwise combination of the UPDATE_OPTION_* flags.
+ */
+int record_metacommit(struct repository *repo,
+ const struct metacommit_data *metacommit,
+ const char* override_change, int options, struct strbuf *err)
+{
+ static const char *msg = "updating change";
+ struct metacommit_data resolved_metacommit;
+ struct string_list changes;
+ struct object_id commit_target;
+ struct ref_transaction *transaction = NULL;
+ struct object_id old_head_working;
+ const struct object_id *old_head;
+ struct change_table chtable;
+ int i;
+ int ret = 0;
+ int force = (options & UPDATE_OPTION_FORCE);
+
+ init_metacommit_data(&resolved_metacommit);
+ string_list_init(&changes, 1);
+
+ change_table_init(&chtable);
+
+ change_table_add_all_visible(&chtable, repo);
+
+ resolve_metacommit(repo, &chtable, metacommit, &resolved_metacommit,
&changes,
+ (options & UPDATE_OPTION_NOAPPEND) == 0);
+
+ if (override_change) {
+ old_head = &old_head_working;
+ string_list_clear(&changes, 0);
+ if (get_oid_committish(override_change, &old_head_working)) {
+ // ...then this is a newly-created change
+ old_head = &null_oid;
+ } else if (!force) {
+ if
(!oid_array_contains_nondestructive(&(resolved_metacommit.replace),
+ &old_head_working)) {
+ // Attempted non-fast-forward change
+ strbuf_addf(err, _("non-fast-forward update to
'%s'"),
+ override_change);
+ ret = -1;
+ goto cleanup;
+ }
+ }
+ // The expected "current" head of the change is stored in the
util pointer
+ string_list_append(&changes, override_change)->util =
(void*)old_head;
+ }
+
+ if (is_nontrivial_metacommit(&resolved_metacommit)) {
+ // If there are any origin or replacement parents, create a new
metacommit
+ // object.
+ if (write_metacommit(repo, &resolved_metacommit,
&commit_target) < 0) {
+ ret = -1;
+ goto cleanup;
+ }
+ } else {
+ // If the metacommit would only contain a content commit, point
to the
+ // commit itself rather than creating a trivial metacommit.
+ oidcpy(&commit_target, &(resolved_metacommit.content));
+ }
+
+ // If a change already exists with this target and we're not forcing an
+ // update to some specific override_change && change, there's nothing
to do.
+ if (!override_change
+ && change_table_has_change_referencing(&chtable,
&commit_target)) {
+ // Not an error
+ goto cleanup;
+ }
+
+ transaction = ref_transaction_begin(err);
+
+ // Update the refs for each affected change
+ if (!transaction) {
+ ret = -1;
+ } else {
+ for (i = 0; i < changes.nr; i++) {
+ struct string_list_item *it = &(changes.items[i]);
+
+ // The expected current head of the change is stored in
the util pointer.
+ // It is null if the change should be newly-created.
+ if (it->util) {
+ if (ref_transaction_update(transaction,
it->string, &commit_target,
+ force ? NULL : it->util, 0, msg, err)) {
+
+ ret = -1;
+ }
+ } else {
+ if (ref_transaction_create(transaction,
it->string,
+ &commit_target, 0, msg, err)) {
+
+ ret = -1;
+ }
+ }
+ }
+
+ if (!ret) {
+ if (ref_transaction_commit(transaction, err)) {
+ ret = -1;
+ }
+ }
+ }
+
+cleanup:
+ ref_transaction_free(transaction);
+ string_list_clear(&changes, 0);
+ clear_metacommit_data(&resolved_metacommit);
+ change_table_clear(&chtable);
+ return ret;
+}
+
+/*
+ * Should be invoked after a command that has "modify" semantics - commands
that
+ * create a new commit based on an old commit and treat the new one as a
+ * replacement for the old one. This method records the replacement in the
+ * change graph, such that a future evolve operation will rebase children of
+ * the old commit onto the new commit.
+ */
+void modify_change(
+ struct repository *repo,
+ const struct object_id *old_commit,
+ const struct object_id *new_commit,
+ struct strbuf *err)
+{
+ struct metacommit_data metacommit;
+
+ init_metacommit_data(&metacommit);
+ oidcpy(&(metacommit.content), new_commit);
+ oid_array_append(&(metacommit.replace), old_commit);
+
+ record_metacommit(repo, &metacommit, NULL, 0, err);
+
+ clear_metacommit_data(&metacommit);
+}
diff --git a/metacommit.h b/metacommit.h
new file mode 100644
index 0000000000..1d4be9cdfb
--- /dev/null
+++ b/metacommit.h
@@ -0,0 +1,39 @@
+#ifndef METACOMMIT_H
+#define METACOMMIT_H
+
+// If specified, non-fast-forward changes are permitted.
+#define UPDATE_OPTION_FORCE 0x0001
+// If specified, no attempt will be made to append to existing changes.
+// Normally, if a metacommit points to a commit in its replace or origin
+// list and an existing change points to that same commit as its content, the
+// new metacommit will attempt to append to that same change. This may replace
+// the commit parent with one or more metacommits from the head of the appended
+// changes. This option disables this behavior, and will always create a new
+// change rather than reusing existing changes.
+#define UPDATE_OPTION_NOAPPEND 0x0002
+
+// Metacommit Data
+
+struct metacommit_data {
+ struct object_id content;
+ struct oid_array replace;
+ struct oid_array origin;
+ int abandoned;
+};
+
+extern void init_metacommit_data(struct metacommit_data *state);
+
+extern void clear_metacommit_data(struct metacommit_data *state);
+
+extern int record_metacommit(struct repository *repo,
+ const struct metacommit_data *metacommit,
+ const char* override_change, int options, struct strbuf *err);
+
+extern void modify_change(struct repository *repo,
+ const struct object_id *old_commit, const struct object_id *new_commit,
+ struct strbuf *err);
+
+extern int write_metacommit(struct repository *repo, struct metacommit_data
*state,
+ struct object_id *result);
+
+#endif
--
2.20.1.321.g9e740568ce-goog
