fast-import: add support for new 'alias' command

fast-export and fast-import have nice --import-marks flags which allow
for incremental migrations.  However, if there is a mark in
fast-export's file of marks without a corresponding mark in the one for
fast-import, then we run the risk that fast-export tries to send new
objects relative to the mark it knows which fast-import does not,
causing fast-import to fail.

This arises in practice when there is a filter of some sort running
between the fast-export and fast-import processes which prunes some
commits programmatically.  Provide such a filter with the ability to
alias pruned commits to their most recent non-pruned ancestor.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Elijah Newren 2019-10-03 13:27:05 -07:00 committed by Junio C Hamano
parent f73b2aba05
commit b8f50e5b60
3 changed files with 79 additions and 10 deletions

View File

@ -337,6 +337,13 @@ and control the current import process. More detailed discussion
`commit` command. This command is optional and is not
needed to perform an import.
`alias`::
Record that a mark refers to a given object without first
creating any new object. Using --import-marks and referring
to missing marks will cause fast-import to fail, so aliases
can provide a way to set otherwise pruned commits to a valid
value (e.g. the nearest non-pruned ancestor).
`checkpoint`::
Forces fast-import to close the current packfile, generate its
unique SHA-1 checksum and index, and start a new packfile.
@ -914,6 +921,21 @@ a data chunk which does not have an LF as its last byte.
+
The `LF` after `<delim> LF` is optional (it used to be required).
`alias`
~~~~~~~
Record that a mark refers to a given object without first creating any
new object.
....
'alias' LF
mark
'to' SP <commit-ish> LF
LF?
....
For a detailed description of `<commit-ish>` see above under `from`.
`checkpoint`
~~~~~~~~~~~~
Forces fast-import to close the current packfile, start a new one, and to

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@ -2491,18 +2491,14 @@ static void parse_from_existing(struct branch *b)
}
}
static int parse_from(struct branch *b)
static int parse_objectish(struct branch *b, const char *objectish)
{
const char *from;
struct branch *s;
struct object_id oid;
if (!skip_prefix(command_buf.buf, "from ", &from))
return 0;
oidcpy(&oid, &b->branch_tree.versions[1].oid);
s = lookup_branch(from);
s = lookup_branch(objectish);
if (b == s)
die("Can't create a branch from itself: %s", b->name);
else if (s) {
@ -2510,8 +2506,8 @@ static int parse_from(struct branch *b)
oidcpy(&b->oid, &s->oid);
oidcpy(&b->branch_tree.versions[0].oid, t);
oidcpy(&b->branch_tree.versions[1].oid, t);
} else if (*from == ':') {
uintmax_t idnum = parse_mark_ref_eol(from);
} else if (*objectish == ':') {
uintmax_t idnum = parse_mark_ref_eol(objectish);
struct object_entry *oe = find_mark(idnum);
if (oe->type != OBJ_COMMIT)
die("Mark :%" PRIuMAX " not a commit", idnum);
@ -2525,13 +2521,13 @@ static int parse_from(struct branch *b)
} else
parse_from_existing(b);
}
} else if (!get_oid(from, &b->oid)) {
} else if (!get_oid(objectish, &b->oid)) {
parse_from_existing(b);
if (is_null_oid(&b->oid))
b->delete = 1;
}
else
die("Invalid ref name or SHA1 expression: %s", from);
die("Invalid ref name or SHA1 expression: %s", objectish);
if (b->branch_tree.tree && !oideq(&oid, &b->branch_tree.versions[1].oid)) {
release_tree_content_recursive(b->branch_tree.tree);
@ -2542,6 +2538,26 @@ static int parse_from(struct branch *b)
return 1;
}
static int parse_from(struct branch *b)
{
const char *from;
if (!skip_prefix(command_buf.buf, "from ", &from))
return 0;
return parse_objectish(b, from);
}
static int parse_objectish_with_prefix(struct branch *b, const char *prefix)
{
const char *base;
if (!skip_prefix(command_buf.buf, prefix, &base))
return 0;
return parse_objectish(b, base);
}
static struct hash_list *parse_merge(unsigned int *count)
{
struct hash_list *list = NULL, **tail = &list, *n;
@ -3087,6 +3103,28 @@ static void parse_progress(void)
skip_optional_lf();
}
static void parse_alias(void)
{
struct object_entry *e;
struct branch b;
skip_optional_lf();
read_next_command();
/* mark ... */
parse_mark();
if (!next_mark)
die(_("Expected 'mark' command, got %s"), command_buf.buf);
/* to ... */
memset(&b, 0, sizeof(b));
if (!parse_objectish_with_prefix(&b, "to "))
die(_("Expected 'to' command, got %s"), command_buf.buf);
e = find_object(&b.oid);
assert(e);
insert_mark(next_mark, e);
}
static char* make_fast_import_path(const char *path)
{
if (!relative_marks_paths || is_absolute_path(path))
@ -3214,6 +3252,8 @@ static int parse_one_feature(const char *feature, int from_stream)
option_import_marks(arg, from_stream, 1);
} else if (skip_prefix(feature, "export-marks=", &arg)) {
option_export_marks(arg);
} else if (!strcmp(feature, "alias")) {
; /* Don't die - this feature is supported */
} else if (!strcmp(feature, "get-mark")) {
; /* Don't die - this feature is supported */
} else if (!strcmp(feature, "cat-blob")) {
@ -3370,6 +3410,8 @@ int cmd_main(int argc, const char **argv)
parse_checkpoint();
else if (!strcmp("done", command_buf.buf))
break;
else if (!strcmp("alias", command_buf.buf))
parse_alias();
else if (starts_with(command_buf.buf, "progress "))
parse_progress();
else if (skip_prefix(command_buf.buf, "feature ", &v))

View File

@ -111,6 +111,10 @@ test_expect_success 'A: create pack from stdin' '
Tag of tag of our lovely commit
EOF
alias
mark :8
to :5
INPUT_END
git fast-import --export-marks=marks.out <input &&
git whatchanged master
@ -195,6 +199,7 @@ test_expect_success 'A: verify marks output' '
:5 $(git rev-parse --verify master^0)
:6 $(git cat-file tag nested | grep object | cut -d" " -f 2)
:7 $(git rev-parse --verify nested)
:8 $(git rev-parse --verify master^0)
EOF
test_cmp expect marks.out
'