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@xxxxxxxxx>
---
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 `<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
diff --git a/fast-import.c b/fast-import.c
index 0042440487..9a12850d16 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;
@@ -3089,6 +3105,28 @@ 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))
@@ -3216,6 +3254,8 @@ 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")) {
@@ -3372,6 +3412,8 @@ 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 <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
'
--
2.23.0.264.gac739dbb79
