From b8f50e5b60e2654fcbf5f72b682635ee2e624923 Mon Sep 17 00:00:00 2001 From: Elijah Newren Date: Thu, 3 Oct 2019 13:27:05 -0700 Subject: 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 Signed-off-by: Junio C Hamano --- Documentation/git-fast-import.txt | 22 ++++++++++++++ fast-import.c | 62 ++++++++++++++++++++++++++++++++------- t/t9300-fast-import.sh | 5 ++++ 3 files changed, 79 insertions(+), 10 deletions(-) diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt index 4977869465..a3f1e0c5e4 100644 --- a/Documentation/git-fast-import.txt +++ b/Documentation/git-fast-import.txt @@ -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 ` 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 LF + LF? +.... + +For a detailed description of `` see above under `from`. + + `checkpoint` ~~~~~~~~~~~~ Forces fast-import to close the current packfile, start a new one, and to diff --git a/fast-import.c b/fast-import.c index 5b9e9e3b02..ac368b3e2b 100644 --- a/fast-import.c +++ b/fast-import.c @@ -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)) diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh index 3ad2b2f1ba..41f2a1dad9 100755 --- a/t/t9300-fast-import.sh +++ b/t/t9300-fast-import.sh @@ -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