Re: [PATCH 08/10] fast-export: add --reference-excluded-parents option
On Sat, Nov 10, 2018 at 10:23:10PM -0800, Elijah Newren wrote:
> git filter-branch has a nifty feature allowing you to rewrite, e.g. just
> the last 8 commits of a linear history
> git filter-branch $OPTIONS HEAD~8..HEAD
>
> If you try the same with git fast-export, you instead get a history of
> only 8 commits, with HEAD~7 being rewritten into a root commit. There
> are two alternatives:
Ah, I think this maybe answers some of my earlier questions, too. You
cannot use fast-import as it stands to do a partial rewrite.
> 1) Don't use the negative revision specification, and when you're
> filtering the output to make modifications to the last 8 commits,
> just be careful to not modify any earlier commits somehow.
>
> 2) First run 'git fast-export --export-marks=somefile HEAD~8', then
> run 'git fast-export --import-marks=somefile HEAD~8..HEAD'.
>
> Both are more error prone than I'd like (the first for obvious reasons;
> with the second option I have sometimes accidentally included too many
> revisions in the first command and then found that the corresponding
> extra revisions were not exported by the second command and thus were
> not modified as I expected). Also, both are poor from a performance
> perspective.
Yeah, this should be O(commits you're touching), and it the current code
does not allow that at all. So I think this feature makes a lot of sense
(it probably _should_ have been the default, but it's a bit late for
that now).
> @@ -638,13 +640,21 @@ static void handle_commit(struct commit *commit, struct
> rev_info *rev,
> unuse_commit_buffer(commit, commit_buffer);
>
> for (i = 0, p = commit->parents; p; p = p->next) {
> - int mark = get_object_mark(&p->item->object);
> - if (!mark)
> + struct object *obj = &p->item->object;
> + int mark = get_object_mark(obj);
> +
> + if (!mark && !reference_excluded_commits)
> continue;
> if (i == 0)
> - printf("from :%d\n", mark);
> + printf("from ");
> + else
> + printf("merge ");
> + if (mark)
> + printf(":%d\n", mark);
> else
> - printf("merge :%d\n", mark);
> + printf("%s\n", sha1_to_hex(anonymize ?
> +anonymize_sha1(&obj->oid) :
> +obj->oid.hash));
> i++;
> }
OK, so this just teaches us to start with the sensible "from" directive.
I think we might be able to do a little more optimization here. If we're
exporting HEAD^..HEAD and there's an object in HEAD^ which is unchanged
in HEAD, I think we'd still print it (because it would not be marked
SHOWN), but we could omit it (by walking the tree of the boundary
commits and marking them shown).
I don't think it's a blocker for what you're doing here, but just a
possible future optimization.
> @@ -925,13 +935,22 @@ static void handle_tags_and_duplicates(struct
> string_list *extras)
> /*
>* Getting here means we have a commit which
>* was excluded by a negative refspec (e.g.
> - * fast-export ^master master). If the user
> + * fast-export ^master master). If we are
> + * referencing excluded commits, set the ref
> + * to the exact commit. Otherwise, the user
>* wants the branch exported but every commit
> - * in its history to be deleted, that sounds
> - * like a ref deletion to me.
> + * in its history to be deleted, which basically
> + * just means deletion of the ref.
>*/
> - printf("reset %s\nfrom %s\n\n",
> -name, sha1_to_hex(null_sha1));
> + if (!reference_excluded_commits) {
> + /* delete the ref */
> + printf("reset %s\nfrom %s\n\n",
> +name, sha1_to_hex(null_sha1));
> + continue;
> + }
> + /* set ref to commit using oid, not mark */
> + printf("reset %s\nfrom %s\n\n", name,
> +sha1_to_hex(commit->object.oid.hash));
OK, and this is basically answering my earlier questions again: yes, you
_would_ want to keep old tags pointing at their commits. But only in
this much more sensible mode.
-Peff
[PATCH 08/10] fast-export: add --reference-excluded-parents option
git filter-branch has a nifty feature allowing you to rewrite, e.g. just
the last 8 commits of a linear history
git filter-branch $OPTIONS HEAD~8..HEAD
If you try the same with git fast-export, you instead get a history of
only 8 commits, with HEAD~7 being rewritten into a root commit. There
are two alternatives:
1) Don't use the negative revision specification, and when you're
filtering the output to make modifications to the last 8 commits,
just be careful to not modify any earlier commits somehow.
2) First run 'git fast-export --export-marks=somefile HEAD~8', then
run 'git fast-export --import-marks=somefile HEAD~8..HEAD'.
Both are more error prone than I'd like (the first for obvious reasons;
with the second option I have sometimes accidentally included too many
revisions in the first command and then found that the corresponding
extra revisions were not exported by the second command and thus were
not modified as I expected). Also, both are poor from a performance
perspective.
Add a new --reference-excluded-parents option which will cause
fast-export to refer to commits outside the specified rev-list-args
range by their sha1sum. Such a stream will only be useful in a
repository which already contains the necessary commits (much like the
restriction imposed when using --no-data).
Signed-off-by: Elijah Newren
---
Documentation/git-fast-export.txt | 16 ++--
builtin/fast-export.c | 42 +++
t/t9350-fast-export.sh| 11
3 files changed, 57 insertions(+), 12 deletions(-)
diff --git a/Documentation/git-fast-export.txt
b/Documentation/git-fast-export.txt
index 677510b7f7..2916096bdd 100644
--- a/Documentation/git-fast-export.txt
+++ b/Documentation/git-fast-export.txt
@@ -110,6 +110,17 @@ marks the same across runs.
the shape of the history and stored tree. See the section on
`ANONYMIZING` below.
+--reference-excluded-parents::
+ By default, running a command such as `git fast-export
+ master~5..master` will not include the commit master\~5 and
+ will make master\~4 no longer have master\~5 as a parent (though
+ both the old master\~4 and new master~4 will have all the same
+ files). Use --reference-excluded-parents to instead have the
+ the stream refer to commits in the excluded range of history
+ by their sha1sum. Note that the resulting stream can only be
+ used by a repository which already contains the necessary
+ parent commits.
+
--refspec::
Apply the specified refspec to each ref exported. Multiple of them can
be specified.
@@ -119,8 +130,9 @@ marks the same across runs.
'git rev-list', that specifies the specific objects and references
to export. For example, `master~10..master` causes the
current master reference to be exported along with all objects
- added since its 10th ancestor commit and all files common to
- master\~9 and master~10.
+ added since its 10th ancestor commit and (unless the
+ --reference-excluded-parents option is specified) all files
+ common to master\~9 and master~10.
EXAMPLES
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 0d0bbd9445..ea9c5b1c00 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -37,6 +37,7 @@ static int fake_missing_tagger;
static int use_done_feature;
static int no_data;
static int full_tree;
+static int reference_excluded_commits;
static struct string_list extra_refs = STRING_LIST_INIT_NODUP;
static struct string_list tag_refs = STRING_LIST_INIT_NODUP;
static struct refspec refspecs = REFSPEC_INIT_FETCH;
@@ -596,7 +597,8 @@ static void handle_commit(struct commit *commit, struct
rev_info *rev,
message += 2;
if (commit->parents &&
- get_object_mark(&commit->parents->item->object) != 0 &&
+ (get_object_mark(&commit->parents->item->object) != 0 ||
+reference_excluded_commits) &&
!full_tree) {
parse_commit_or_die(commit->parents->item);
diff_tree_oid(get_commit_tree_oid(commit->parents->item),
@@ -638,13 +640,21 @@ static void handle_commit(struct commit *commit, struct
rev_info *rev,
unuse_commit_buffer(commit, commit_buffer);
for (i = 0, p = commit->parents; p; p = p->next) {
- int mark = get_object_mark(&p->item->object);
- if (!mark)
+ struct object *obj = &p->item->object;
+ int mark = get_object_mark(obj);
+
+ if (!mark && !reference_excluded_commits)
continue;
if (i == 0)
- printf("from :%d\n", mark);
+ printf("from ");
+ else
+ printf("merge ");
+ if (mark)
+ printf(":%d\n", mark);
else
-
