fast-import: fix lookup for new commits

From: Marc Becker <[email protected]>

Queries for commits created during the same 'git fast-import' session result in a crash:
< reset refs/heads/newbranch
< from <new-commit-oid>
> fatal: not a valid commit: <new-commit-oid>

Getting file content for commit has no issue (working implementation):
< ls <new-commit-oid> file-in-new-commit.txt
> {file content}

During import, new objects may not (yet) be reachable via the ODB layer. Try to resolve requested tag/commit via object cache first to avoid crash and (eventually) improve lookup speed.

---
fast-import: fix lookup for new commits

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2252%2Fbecm%2Ffix-fast-import-commit-from-existing-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2252/becm/fix-fast-import-commit-from-existing-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/2252

 builtin/fast-import.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

index fbd919982c..4b93148551 100644
@@ -292,6 +292,8 @@ static void fast_import_state_init(struct fast_import_state *state,
 	state->option = option;
 }
 
+static struct object_entry *dereference(struct object_entry *oe, struct object_id *oid);
+
 static void parse_argv(struct fast_import_state *state);
 static void parse_get_mark(struct fast_import_state *state, const char *p);
 static void parse_cat_blob(struct fast_import_state *state, const char *p);

@@ -2658,12 +2660,20 @@ static void parse_from_existing(struct branch *b)
 		oidclr(&b->branch_tree.versions[1].oid, the_repository->hash_algo);
 	} else {
 		unsigned long size;
-		size_t size_st = 0;
 		char *buf;
+		struct object_entry *e = find_object(&b->oid);
 
-		buf = odb_read_object_peeled(the_repository->objects, &b->oid,
-					     OBJ_COMMIT, &size_st, &b->oid);
-		size = cast_size_t_to_ulong(size_st);
+		while (e && e->type == OBJ_TAG)
+			e = dereference(e, &b->oid);
+
+		if (e && e->type == OBJ_COMMIT && e->pack_id != MAX_PACK_ID) {
+			buf = gfi_unpack_entry(e, &size);
+		} else {
+			size_t size_st = 0;
+			buf = odb_read_object_peeled(the_repository->objects, &b->oid,
+						     OBJ_COMMIT, &size_st, &b->oid);
+			size = cast_size_t_to_ulong(size_st);
+		}
 		parse_from_commit(b, buf, size);
 		free(buf);
 	}

base-commit: 6de20f6092dcf9bdb1c8efe03db4b70c82b423dd

gitgitgadget

Hello Marc,

Sorry for the noise, my first mail lost its In-Reply-To header on the way, so it is not in this thread. Resending the same review here.

I tried this on top of 6de20f609 with DEVELOPER=1 and did not get warnings.

I was able to repro this. With the patch fsck is clean and it works nicely. Same goes for "commit" with "from <new-oid>", a tag made in the same session, and a tag of a tag. Existing commits and tags and "from <blob>" behave like before.

One small nitpick: there is a double space in "'git fast-import' session".

Did you measure this? If not, maybe drop it or say it is only a possible side effect.

This is over 80 columns, can it be wrapped like the definition?

I could not find a test for this. Can you add one to t9300? You can get the new oid with get-mark and use it in a "reset ... from <oid>" in the same stream.

Thanks,
Aniket

From: Marc Becker <[email protected]>

Queries for commits created during the same 'git fast-import' session result in a crash:
< reset refs/heads/newbranch
< from <new-commit-oid>
> fatal: not a valid commit: <new-commit-oid>

Getting file content for commit has no issue (working implementation):
< ls <new-commit-oid> file-in-new-commit.txt
> {file content}

During import, new objects may not (yet) be reachable via the ODB layer. Try to resolve requested tag/commit via object cache first to avoid crash.
Add test to 't/t9300.sh' with references to a pending tag and commit.

---
fast-import: fix lookup for new commits

Changes since v1:

* address notes regarding commit message
* stick to line length in new code
* add test with (fixed) pending references (files for SHA1 and SHA256, no coproc in sh, avoid named pipes)

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2252%2Fbecm%2Ffix-fast-import-commit-from-existing-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2252/becm/fix-fast-import-commit-from-existing-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/2252

Range-diff vs v1:

1: 4e50f63354 ! 1: d834e2fc47 fast-import: fix lookup for new commits

     @@ Metadata
      Author: Marc Becker <[email protected]>
      
       ## Commit message ##
     -    fast-import: fix lookup for new commits
     +    fast-import: fix lookup for new commits and tags
      
     -    Queries for commits created during the same 'git fast-import'  session
     +    Queries for commits created during the same 'git fast-import' session
          result in a crash:
              < reset refs/heads/newbranch
              < from <new-commit-oid>
     @@ Commit message
      
          During import, new objects may not (yet) be reachable via the ODB layer.
          Try to resolve requested tag/commit via object cache first
     -    to avoid crash and (eventually) improve lookup speed.
     +    to avoid crash.
     +    Add test to 't/t9300.sh' with references to a pending tag and commit.
      
          Signed-off-by: Marc Becker <[email protected]>
      
     @@ builtin/fast-import.c: static void fast_import_state_init(struct fast_import_sta
       	state->option = option;
       }
       
     -+static struct object_entry *dereference(struct object_entry *oe, struct object_id *oid);
     ++static struct object_entry *dereference(struct object_entry *oe,
     ++					struct object_id *oid);
      +
       static void parse_argv(struct fast_import_state *state);
       static void parse_get_mark(struct fast_import_state *state, const char *p);
     @@ builtin/fast-import.c: static void parse_from_existing(struct branch *b)
       		parse_from_commit(b, buf, size);
       		free(buf);
       	}
     +
     + ## t/t9300-fast-import.sh ##
     +@@ t/t9300-fast-import.sh: test_expect_success 'Y: rewrite submodules' '
     + 	)
     + '
     + 
     ++cat >Y-reference-pending-sha256 <<\Y_INPUT_END
     ++commit refs/heads/main
     ++committer A U Thor <[email protected]> 1712563200 +0000
     ++data 14
     ++commit message
     ++M 644 inline test file
     ++data 14
     ++dummy content
     ++
     ++tag newtag
     ++from 17e650f097a4db6fe069c96935360d3ccc9b35c4018728c5f311a4217c2ced3d
     ++tagger A U Thor <[email protected]> 1712563300 +0000
     ++data 11
     ++tag message
     ++# no emty line after tag data!
     ++reset refs/heads/other
     ++from 85edc5eac315bc680677b2fc71622bd77476f057eb8dc8ed6a497803a24f1f46
     ++
     ++commit refs/heads/further
     ++committer A U Thor <[email protected]> 1712563400 +0000
     ++data 21
     ++what about 2nd commit
     ++from 17e650f097a4db6fe069c96935360d3ccc9b35c4018728c5f311a4217c2ced3d
     ++M 644 inline other test file
     ++data 19
     ++more dummy content
     ++
     ++done
     ++Y_INPUT_END
     ++
     ++cat >Y-reference-pending-sha1 <<\Y_INPUT_END
     ++commit refs/heads/main
     ++committer A U Thor <[email protected]> 1712563200 +0000
     ++data 14
     ++commit message
     ++M 644 inline test file
     ++data 14
     ++dummy content
     ++
     ++tag newtag
     ++from 85b46dd918355ff17b4109ec738723d42f235a04
     ++tagger A U Thor <[email protected]> 1712563300 +0000
     ++data 11
     ++tag message
     ++# no emty line after tag data!
     ++reset refs/heads/other
     ++from ec6c4db71feb5f66615214dad2324ce030e777a7
     ++
     ++commit refs/heads/further
     ++committer A U Thor <[email protected]> 1712563400 +0000
     ++data 21
     ++what about 2nd commit
     ++from 85b46dd918355ff17b4109ec738723d42f235a04
     ++M 644 inline other test file
     ++data 19
     ++more dummy content
     ++
     ++done
     ++Y_INPUT_END
     ++
     ++test_expect_success 'Y: reference pending tag or commit' '
     ++	git init reference-pending &&
     ++	(
     ++		cd reference-pending &&
     ++		git fast-import < "../Y-reference-pending-$(git rev-parse --show-object-format)"
     ++	)
     ++'
     ++
     + test_done

 builtin/fast-import.c  | 19 +++++++++---
 t/t9300-fast-import.sh | 68 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 4 deletions(-)

index fbd919982c..574a03c484 100644
@@ -292,6 +292,9 @@ static void fast_import_state_init(struct fast_import_state *state,
 	state->option = option;
 }
 
+static struct object_entry *dereference(struct object_entry *oe,
+					struct object_id *oid);
+
 static void parse_argv(struct fast_import_state *state);
 static void parse_get_mark(struct fast_import_state *state, const char *p);
 static void parse_cat_blob(struct fast_import_state *state, const char *p);

@@ -2658,12 +2661,20 @@ static void parse_from_existing(struct branch *b)
 		oidclr(&b->branch_tree.versions[1].oid, the_repository->hash_algo);
 	} else {
 		unsigned long size;
-		size_t size_st = 0;
 		char *buf;
+		struct object_entry *e = find_object(&b->oid);
 
-		buf = odb_read_object_peeled(the_repository->objects, &b->oid,
-					     OBJ_COMMIT, &size_st, &b->oid);
-		size = cast_size_t_to_ulong(size_st);
+		while (e && e->type == OBJ_TAG)
+			e = dereference(e, &b->oid);
+
+		if (e && e->type == OBJ_COMMIT && e->pack_id != MAX_PACK_ID) {
+			buf = gfi_unpack_entry(e, &size);
+		} else {
+			size_t size_st = 0;
+			buf = odb_read_object_peeled(the_repository->objects, &b->oid,
+						     OBJ_COMMIT, &size_st, &b->oid);
+			size = cast_size_t_to_ulong(size_st);
+		}
 		parse_from_commit(b, buf, size);
 		free(buf);
 	}

base-commit: 6de20f6092dcf9bdb1c8efe03db4b70c82b423dd

gitgitgadget

"Marc Becker via GitGitGadget" <[email protected]> writes:

The patch text seems to make sense, but ...

Should it say "sometimes results in a crash"? It is not like that no queries for commits can ever be made before the session gets closed, right?

... what do you mean by "(working implementation)" here? Do you mean that without your patch applied, neither commits nor blobs can be read, and with the patch applied we get a "working implementation" and blobs can be read? Or do you mean that objects other than commits do not have such a problem?

Or do you mean the current code does not allow reading commits but everything else it does allow reading? If so, such a description should be followed by why commit alone is so special, or put it differently, why blobs can be accessed just fine. Otherwise, saying that getting file content would work fine only confuses readers without adding much value to them.

This "may not (yet)" is very believable; I would be very surprised if we were holding any and all object data we were fed in core without flushing to the ODB, but depending on the timing of your query, necessary objects may or may not have been flushed. Is that what you meant by "may not (yet)" here? If so, that confirms my "sometimes results in a crash" above, right?

Here is what my assistant produced trying to guess what the commit wanted to say. I do not know how close it is to what you wanted to say, but if the change were explained like this, it may have been easier to understand. At least, failures for commit vs success with blobs you hinted at is explained sufficiently.

Of course, my assistant may be totally off the mark and the following may not explain what you wanted to do at all. I dunno.

fast-import: allow 'from' to reference new commits and tags by oid

During a 'git fast-import' session, newly created objects are written to an in-progress packfile and recorded in fast-import's internal object table. Until a 'checkpoint' command or the end of the session finalizes and indexes that packfile, these objects are not visible to the repository's object database via odb_read_object_peeled().

Commands such as 'ls' (via parse_treeish_dataref() and dereference()) and 'cat-blob' already account for this when given a hex object name:
they look up the object in fast-import's internal object table with find_object() first and read it from the in-progress packfile with gfi_unpack_entry() when its '.pack_id' is not MAX_PACK_ID.

By contrast, when 'from <committish>' (in a 'commit' or 'reset' command) is given a hex object name instead of a mark or branch name, parse_objectish() parses the hex string into 'b->oid' and calls parse_from_existing(), which unconditionally looks up the object via odb_read_object_peeled(). If the object is a commit or tag created in the current pack cycle, odb_read_object_peeled() returns NULL and fast-import dies with "fatal: not a valid commit: <oid>".

Teach parse_from_existing() to look up 'b->oid' with find_object() first, peel any tag objects in the object table using dereference(), and unpack the target commit with gfi_unpack_entry() if it resides in the in-progress packfile, before falling back to odb_read_object_peeled() for objects in the repository's object database.

From: Marc Becker <[email protected]>

During a 'git fast-import' session, newly created objects are written to an in-progress packfile and recorded in fast-import's internal object table. Until a 'checkpoint' command or the end of the session finalizes and indexes that packfile, these objects are not visible to the repository's object database via odb_read_object_peeled().

Commands such as 'ls' (via parse_treeish_dataref() and dereference()) and 'cat-blob' already account for this when given a hex object name:
they look up the object in fast-import's internal object table with find_object() first and read it from the in-progress packfile with gfi_unpack_entry() when its '.pack_id' is not MAX_PACK_ID.

By contrast, when 'from <committish>' (in a 'commit' or 'reset' command) is given a hex object name instead of a mark or branch name, parse_objectish() parses the hex string into 'b->oid' and calls parse_from_existing(), which unconditionally looks up the object via odb_read_object_peeled(). If the object is a commit or tag created in the current pack cycle, odb_read_object_peeled() returns NULL and fast-import dies with "fatal: not a valid commit: <oid>".

Teach parse_from_existing() to look up 'b->oid' with find_object() first, peel any tag objects in the object table using dereference(), and unpack the target commit with gfi_unpack_entry() if it resides in the in-progress packfile, before falling back to odb_read_object_peeled() for objects in the repository's object database.

---
fast-import: fix lookup for new commits

Changes since v2:

* use LLM-generated commit message (description is on point) by Junio
* provide hash-specific OIDs in test code via test_oid

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2252%2Fbecm%2Ffix-fast-import-commit-from-existing-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2252/becm/fix-fast-import-commit-from-existing-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/2252

Range-diff vs v2:

1: d834e2fc47 ! 1: 25113432c6 fast-import: fix lookup for new commits and tags

     @@ Metadata
      Author: Marc Becker <[email protected]>
      
       ## Commit message ##
     -    fast-import: fix lookup for new commits and tags
     +    fast-import: allow 'from' to reference new commits and tags by oid
      
     -    Queries for commits created during the same 'git fast-import' session
     -    result in a crash:
     -        < reset refs/heads/newbranch
     -        < from <new-commit-oid>
     -        > fatal: not a valid commit: <new-commit-oid>
     +    During a 'git fast-import' session, newly created objects are written
     +    to an in-progress packfile and recorded in fast-import's internal
     +    object table.  Until a 'checkpoint' command or the end of the session
     +    finalizes and indexes that packfile, these objects are not visible to
     +    the repository's object database via odb_read_object_peeled().
      
     -    Getting file content for commit has no issue (working implementation):
     -        < ls <new-commit-oid> file-in-new-commit.txt
     -        > {file content}
     +    Commands such as 'ls' (via parse_treeish_dataref() and dereference())
     +    and 'cat-blob' already account for this when given a hex object name:
     +    they look up the object in fast-import's internal object table with
     +    find_object() first and read it from the in-progress packfile with
     +    gfi_unpack_entry() when its '.pack_id' is not MAX_PACK_ID.
      
     -    During import, new objects may not (yet) be reachable via the ODB layer.
     -    Try to resolve requested tag/commit via object cache first
     -    to avoid crash.
     -    Add test to 't/t9300.sh' with references to a pending tag and commit.
     +    By contrast, when 'from <committish>' (in a 'commit' or 'reset'
     +    command) is given a hex object name instead of a mark or branch name,
     +    parse_objectish() parses the hex string into 'b->oid' and calls
     +    parse_from_existing(), which unconditionally looks up the object via
     +    odb_read_object_peeled().  If the object is a commit or tag created in
     +    the current pack cycle, odb_read_object_peeled() returns NULL and
     +    fast-import dies with "fatal: not a valid commit: <oid>".
     +
     +    Teach parse_from_existing() to look up 'b->oid' with find_object()
     +    first, peel any tag objects in the object table using dereference(),
     +    and unpack the target commit with gfi_unpack_entry() if it resides in
     +    the in-progress packfile, before falling back to
     +    odb_read_object_peeled() for objects in the repository's object
     +    database.
      
          Signed-off-by: Marc Becker <[email protected]>
      
     @@ t/t9300-fast-import.sh: test_expect_success 'Y: rewrite submodules' '
       	)
       '
       
     -+cat >Y-reference-pending-sha256 <<\Y_INPUT_END
     -+commit refs/heads/main
     -+committer A U Thor <[email protected]> 1712563200 +0000
     -+data 14
     -+commit message
     -+M 644 inline test file
     -+data 14
     -+dummy content
     -+
     -+tag newtag
     -+from 17e650f097a4db6fe069c96935360d3ccc9b35c4018728c5f311a4217c2ced3d
     -+tagger A U Thor <[email protected]> 1712563300 +0000
     -+data 11
     -+tag message
     -+# no emty line after tag data!
     -+reset refs/heads/other
     -+from 85edc5eac315bc680677b2fc71622bd77476f057eb8dc8ed6a497803a24f1f46
     -+
     -+commit refs/heads/further
     -+committer A U Thor <[email protected]> 1712563400 +0000
     -+data 21
     -+what about 2nd commit
     -+from 17e650f097a4db6fe069c96935360d3ccc9b35c4018728c5f311a4217c2ced3d
     -+M 644 inline other test file
     -+data 19
     -+more dummy content
     -+
     -+done
     -+Y_INPUT_END
     -+
     -+cat >Y-reference-pending-sha1 <<\Y_INPUT_END
     -+commit refs/heads/main
     -+committer A U Thor <[email protected]> 1712563200 +0000
     -+data 14
     -+commit message
     -+M 644 inline test file
     -+data 14
     -+dummy content
     -+
     -+tag newtag
     -+from 85b46dd918355ff17b4109ec738723d42f235a04
     -+tagger A U Thor <[email protected]> 1712563300 +0000
     -+data 11
     -+tag message
     -+# no emty line after tag data!
     -+reset refs/heads/other
     -+from ec6c4db71feb5f66615214dad2324ce030e777a7
     -+
     -+commit refs/heads/further
     -+committer A U Thor <[email protected]> 1712563400 +0000
     -+data 21
     -+what about 2nd commit
     -+from 85b46dd918355ff17b4109ec738723d42f235a04
     -+M 644 inline other test file
     -+data 19
     -+more dummy content
     -+
     -+done
     -+Y_INPUT_END
     -+
      +test_expect_success 'Y: reference pending tag or commit' '
     ++	test_oid_cache <<-EOF &&
     ++		pending_commit sha1:85b46dd918355ff17b4109ec738723d42f235a04
     ++		pending_commit sha256:17e650f097a4db6fe069c96935360d3ccc9b35c4018728c5f311a4217c2ced3d
     ++		pending_tag sha1:ec6c4db71feb5f66615214dad2324ce030e777a7
     ++		pending_tag sha256:85edc5eac315bc680677b2fc71622bd77476f057eb8dc8ed6a497803a24f1f46
     ++		EOF
     ++
      +	git init reference-pending &&
      +	(
      +		cd reference-pending &&
     -+		git fast-import < "../Y-reference-pending-$(git rev-parse --show-object-format)"
     ++		git fast-import <<-EOF
     ++			commit refs/heads/main
     ++			committer A U Thor <[email protected]> 1712563200 +0000
     ++			data 14
     ++			commit message
     ++			M 644 inline test file
     ++			data 14
     ++			dummy content
     ++
     ++			tag newtag
     ++			from $(test_oid pending_commit)
     ++			tagger A U Thor <[email protected]> 1712563300 +0000
     ++			data 11
     ++			tag message
     ++			# no emty line after tag data!
     ++			reset refs/heads/other
     ++			from $(test_oid pending_tag)
     ++
     ++			commit refs/heads/further
     ++			committer A U Thor <[email protected]> 1712563400 +0000
     ++			data 21
     ++			what about 2nd commit
     ++			from $(test_oid pending_commit)
     ++			M 644 inline other test file
     ++			data 19
     ++			more dummy content
     ++
     ++			done
     ++			EOF
      +	)
      +'
      +

 builtin/fast-import.c  | 19 +++++++++++++++----
 t/t9300-fast-import.sh | 43 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 4 deletions(-)

index fbd919982c..574a03c484 100644
@@ -292,6 +292,9 @@ static void fast_import_state_init(struct fast_import_state *state,
 	state->option = option;
 }
 
+static struct object_entry *dereference(struct object_entry *oe,
+					struct object_id *oid);
+
 static void parse_argv(struct fast_import_state *state);
 static void parse_get_mark(struct fast_import_state *state, const char *p);
 static void parse_cat_blob(struct fast_import_state *state, const char *p);

@@ -2658,12 +2661,20 @@ static void parse_from_existing(struct branch *b)
 		oidclr(&b->branch_tree.versions[1].oid, the_repository->hash_algo);
 	} else {
 		unsigned long size;
-		size_t size_st = 0;
 		char *buf;
+		struct object_entry *e = find_object(&b->oid);
 
-		buf = odb_read_object_peeled(the_repository->objects, &b->oid,
-					     OBJ_COMMIT, &size_st, &b->oid);
-		size = cast_size_t_to_ulong(size_st);
+		while (e && e->type == OBJ_TAG)
+			e = dereference(e, &b->oid);
+
+		if (e && e->type == OBJ_COMMIT && e->pack_id != MAX_PACK_ID) {
+			buf = gfi_unpack_entry(e, &size);
+		} else {
+			size_t size_st = 0;
+			buf = odb_read_object_peeled(the_repository->objects, &b->oid,
+						     OBJ_COMMIT, &size_st, &b->oid);
+			size = cast_size_t_to_ulong(size_st);
+		}
 		parse_from_commit(b, buf, size);
 		free(buf);
 	}

base-commit: 6de20f6092dcf9bdb1c8efe03db4b70c82b423dd

gitgitgadget

From: Marc Becker <[email protected]>

During a 'git fast-import' session, newly created objects are written to an in-progress packfile and recorded in fast-import's internal object table. Until a 'checkpoint' command or the end of the session finalizes and indexes that packfile, these objects are not visible to the repository's object database via odb_read_object_peeled().

Commands such as 'ls' (via parse_treeish_dataref() and dereference()) and 'cat-blob' already account for this when given a hex object name:
they look up the object in fast-import's internal object table with find_object() first and read it from the in-progress packfile with gfi_unpack_entry() when its '.pack_id' is not MAX_PACK_ID.

By contrast, when 'from <committish>' (in a 'commit' or 'reset' command) is given a hex object name instead of a mark or branch name, parse_objectish() parses the hex string into 'b->oid' and calls parse_from_existing(), which unconditionally looks up the object via odb_read_object_peeled(). If the object is a commit or tag created in the current pack cycle, odb_read_object_peeled() returns NULL and fast-import dies with "fatal: not a valid commit: <oid>".

Teach parse_from_existing() to look up 'b->oid' with find_object() first, peel any tag objects in the object table using dereference(), and unpack the target commit with gfi_unpack_entry() if it resides in the in-progress packfile, before falling back to odb_read_object_peeled() for objects in the repository's object database.

---
fast-import: fix lookup for new commits

Changes since v3:

* align here-doc indention in test with expected style

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2252%2Fbecm%2Ffix-fast-import-commit-from-existing-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2252/becm/fix-fast-import-commit-from-existing-v4
Pull-Request: https://github.com/gitgitgadget/git/pull/2252

Range-diff vs v3:

1: 25113432c6 ! 1: 0daef81925 fast-import: allow 'from' to reference new commits and tags by oid

     @@ t/t9300-fast-import.sh: test_expect_success 'Y: rewrite submodules' '
       
      +test_expect_success 'Y: reference pending tag or commit' '
      +	test_oid_cache <<-EOF &&
     -+		pending_commit sha1:85b46dd918355ff17b4109ec738723d42f235a04
     -+		pending_commit sha256:17e650f097a4db6fe069c96935360d3ccc9b35c4018728c5f311a4217c2ced3d
     -+		pending_tag sha1:ec6c4db71feb5f66615214dad2324ce030e777a7
     -+		pending_tag sha256:85edc5eac315bc680677b2fc71622bd77476f057eb8dc8ed6a497803a24f1f46
     -+		EOF
     ++	pending_commit sha1:85b46dd918355ff17b4109ec738723d42f235a04
     ++	pending_commit sha256:17e650f097a4db6fe069c96935360d3ccc9b35c4018728c5f311a4217c2ced3d
     ++	pending_tag sha1:ec6c4db71feb5f66615214dad2324ce030e777a7
     ++	pending_tag sha256:85edc5eac315bc680677b2fc71622bd77476f057eb8dc8ed6a497803a24f1f46
     ++	EOF
      +
      +	git init reference-pending &&
      +	(
      +		cd reference-pending &&
      +		git fast-import <<-EOF
     -+			commit refs/heads/main
     -+			committer A U Thor <[email protected]> 1712563200 +0000
     -+			data 14
     -+			commit message
     -+			M 644 inline test file
     -+			data 14
     -+			dummy content
     ++		commit refs/heads/main
     ++		committer A U Thor <[email protected]> 1712563200 +0000
     ++		data 14
     ++		commit message
     ++		M 644 inline test file
     ++		data 14
     ++		dummy content
      +
     -+			tag newtag
     -+			from $(test_oid pending_commit)
     -+			tagger A U Thor <[email protected]> 1712563300 +0000
     -+			data 11
     -+			tag message
     -+			# no emty line after tag data!
     -+			reset refs/heads/other
     -+			from $(test_oid pending_tag)
     ++		tag newtag
     ++		from $(test_oid pending_commit)
     ++		tagger A U Thor <[email protected]> 1712563300 +0000
     ++		data 11
     ++		tag message
     ++		# no emty line after tag data!
     ++		reset refs/heads/other
     ++		from $(test_oid pending_tag)
      +
     -+			commit refs/heads/further
     -+			committer A U Thor <[email protected]> 1712563400 +0000
     -+			data 21
     -+			what about 2nd commit
     -+			from $(test_oid pending_commit)
     -+			M 644 inline other test file
     -+			data 19
     -+			more dummy content
     ++		commit refs/heads/further
     ++		committer A U Thor <[email protected]> 1712563400 +0000
     ++		data 21
     ++		what about 2nd commit
     ++		from $(test_oid pending_commit)
     ++		M 644 inline other test file
     ++		data 19
     ++		more dummy content
      +
     -+			done
     -+			EOF
     ++		done
     ++		EOF
      +	)
      +'
      +

 builtin/fast-import.c  | 19 +++++++++++++++----
 t/t9300-fast-import.sh | 43 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 4 deletions(-)

index fbd919982c..574a03c484 100644
@@ -292,6 +292,9 @@ static void fast_import_state_init(struct fast_import_state *state,
 	state->option = option;
 }
 
+static struct object_entry *dereference(struct object_entry *oe,
+					struct object_id *oid);
+
 static void parse_argv(struct fast_import_state *state);
 static void parse_get_mark(struct fast_import_state *state, const char *p);
 static void parse_cat_blob(struct fast_import_state *state, const char *p);

@@ -2658,12 +2661,20 @@ static void parse_from_existing(struct branch *b)
 		oidclr(&b->branch_tree.versions[1].oid, the_repository->hash_algo);
 	} else {
 		unsigned long size;
-		size_t size_st = 0;
 		char *buf;
+		struct object_entry *e = find_object(&b->oid);
 
-		buf = odb_read_object_peeled(the_repository->objects, &b->oid,
-					     OBJ_COMMIT, &size_st, &b->oid);
-		size = cast_size_t_to_ulong(size_st);
+		while (e && e->type == OBJ_TAG)
+			e = dereference(e, &b->oid);
+
+		if (e && e->type == OBJ_COMMIT && e->pack_id != MAX_PACK_ID) {
+			buf = gfi_unpack_entry(e, &size);
+		} else {
+			size_t size_st = 0;
+			buf = odb_read_object_peeled(the_repository->objects, &b->oid,
+						     OBJ_COMMIT, &size_st, &b->oid);
+			size = cast_size_t_to_ulong(size_st);
+		}
 		parse_from_commit(b, buf, size);
 		free(buf);
 	}

base-commit: 6de20f6092dcf9bdb1c8efe03db4b70c82b423dd

gitgitgadget

Thanks. This round I have nothing more to add.

Will queue.