Shawn O. PearceIf we are exporting a commit which has no parents we may be doing it to a branch that already exists, causing fast-import to assume the branch's current revision should be the sole parent of the new commit. This can cause `git fast-export | git fast-import` to produce an incorrect graph for:
A-------M----o------o refs/heads/master
/
B-+In this graph A and B are initial commits (no parents) but if A was output first to refs/heads/master and then B is output fast-import would assume the graph was this instead:
A-------M----o------o refs/heads/master
\ /
+-B-+Which would cause B, M, and all later commits to have a different SHA-1, and obviously be quite a different graph.
Sending a reset command prior to B informs fast-import to clear the implied parent of A, allowing B to remain an initial commit.
Reported-by: Ben Lynn <benlynn@gmail.com> Deemed-obviously-correct-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Shawn O. Pearce <spearce@spearce.org> --- builtin-fast-export.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)
Show changes to builtin-fast-export.c +2 −0
diff --git a/builtin-fast-export.c b/builtin-fast-export.c index 1dfc01e..d0a462f 100644 --- a/builtin-fast-export.c +++ b/builtin-fast-export.c @@ -188,6 +188,8 @@ static void handle_commit(struct commit *commit, struct rev_info *rev) mark_object(&commit->object); if (!is_encoding_utf8(encoding)) reencoded = reencode_string(message, "UTF-8", encoding); + if (!commit->parents) + printf("reset %s\n", (const char*)commit->util); printf("commit %s\nmark :%d\n%.*s\n%.*s\ndata %u\n%s", (const char *)commit->util, last_idnum, (int)(author_end - author), author,
-- 1.5.6.rc2.165.g2a0cc