[PATCH v2 0/3] Re-fix rebase -i with SHA-1 collisions

Triggered by one of brian's SHA-256 patch series, I looked at the reason why the SHA-1 collision test case passed when it shouldn't. Turns out that the regression test was not quite thorough enough, and the interactive rebase did regress recently.

While in the area, I realized that the same bug exists in the code backing the rebase.missingCommitsCheck feature: the backed-up todo list uses shortened commit IDs that may very well become ambiguous during the rebase. For good measure, this patch series fixes that, too.

Finally, I saw that git rebase --edit-todo reported the line in an awkward, maybe even incorrect, way when there was an ambiguous commit ID, and I also fixed that.

To make sure that the code can be easily adapted to SHA-256 after these patches, I actually already made those adjustments on top and offered them up at https://github.com/bk2204/git/pull/1.

Changes since v1:

 * Turned the error condition when parsing the todo list with just-expanded
   commit IDs failed into a BUG().

Johannes Schindelin (3):
  parse_insn_line(): improve error message when parsing failed
  rebase -i: re-fix short SHA-1 collision
  rebase -i: also avoid SHA-1 collisions with missingCommitsCheck

 rebase-interactive.c          |  8 +++++---
 sequencer.c                   | 18 ++++++++++++++----
 t/t3404-rebase-interactive.sh | 17 +++++++++++++++--
 3 files changed, 34 insertions(+), 9 deletions(-)

base-commit: d0654dc308b0ba76dd8ed7bbb33c8d8f7aacd783
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-529%2Fdscho%2Fre-fix-rebase-i-with-sha-collisions-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-529/dscho/re-fix-rebase-i-with-sha-collisions-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/529

Range-diff vs v1:

 1:  2ae2e435b0 = 1:  2ae2e435b0 parse_insn_line(): improve error message when parsing failed
 2:  ad50cd1b92 ! 2:  102fa568dc rebase -i: re-fix short SHA-1 collision
     @@ -66,12 +66,9 @@
      +	strbuf_swap(&new_todo.buf, &buf2);
      +	strbuf_release(&buf2);
      +	new_todo.total_nr -= new_todo.nr;
     -+	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0) {
     -+		fprintf(stderr, _(edit_todo_list_advice));
     -+		checkout_onto(r, opts, onto_name, &onto->object.oid, orig_head);
     -+		todo_list_release(&new_todo);
     -+		return error(_("invalid todo list after expanding IDs"));
     -+	}
     ++	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0)
     ++		BUG("invalid todo list after expanding IDs:\n%s",
     ++		    new_todo.buf.buf);
      +
       	if (opts->allow_ff && skip_unnecessary_picks(r, &new_todo, &oid)) {
       		todo_list_release(&new_todo);
 3:  e7d9ea8992 = 3:  486e9413a6 rebase -i: also avoid SHA-1 collisions with missingCommitsCheck