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From: Elijah Newren <newren@gmail.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>,
	Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH 03/10] merge-ort: implement unique_path() helper
Date: Wed, 30 Dec 2020 07:10:17 -0800
Message-ID: <CABPp-BF37UeBdF4T68rvOaFRtPyZ2uoUSe48V4K8CUigy77CfA@mail.gmail.com> (raw)
In-Reply-To: <3a07f700-18fc-9f4e-3117-41e534d737b0@gmail.com>

On Wed, Dec 30, 2020 at 6:16 AM Derrick Stolee <stolee@gmail.com> wrote:
>
> On 12/18/2020 12:51 AM, Elijah Newren via GitGitGadget wrote:
> > From: Elijah Newren <newren@gmail.com>
> >
> > Implement unique_path(), based on the one from merge-recursive.c.  It is
> > simplified, however, due to: (1) using strmaps, and (2) the fact that
> > merge-ort lets the checkout codepath handle possible collisions with the
> > working tree means that other code locations don't have to.
> >
> > Signed-off-by: Elijah Newren <newren@gmail.com>
> > ---
> >  merge-ort.c | 25 ++++++++++++++++++++++++-
> >  1 file changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/merge-ort.c b/merge-ort.c
> > index d300a02810e..1adc27a11bc 100644
> > --- a/merge-ort.c
> > +++ b/merge-ort.c
> > @@ -343,11 +343,34 @@ static void path_msg(struct merge_options *opt,
> >       strbuf_addch(sb, '\n');
> >  }
> >
> > +/* add a string to a strbuf, but converting "/" to "_" */
> > +static void add_flattened_path(struct strbuf *out, const char *s)
> > +{
> > +     size_t i = out->len;
> > +     strbuf_addstr(out, s);
> > +     for (; i < out->len; i++)
> > +             if (out->buf[i] == '/')
> > +                     out->buf[i] = '_';
> > +}
> > +
>
> Thank you for pointing out that you based your code on merge-recursive.c.
> I see that this implementation is identical to the one there. I question
> whether this causes collisions in a problematic way, when "a/b/c" and
> "a_b_c" both exist in a tree.
>
> To avoid such a problem, we'd likely need to also expand "_" to "__" or
> similar. This might never actually affect any users because of the
> strange filename matches _and_ we need to be in a directory/file conflict.
>
> And maybe it's not a hole at all? If it is, we can consider patching or
> at least documenting the problem.

add_flattened_path() can certainly result in a collision, regardless
of whether the char *s parameter has any '/' characters in it.  For
example, if you are trying to get a unique path associated with
builtin/commit-graph.c due to changes from the 'next' branch side of
the merge, and builtin/commit-graph.c~next already exists, then you
have a collision.  It's actually pretty rare that the parameter would
have any '/' characters at all, since it's pretty rare for me to see
folks (other than Junio) use hierarchical branch names.  But if the
branch name were ds/line-log-on-bloom, then the provisional filename
would be builtin/commit-graph.c~ds_line-log-on-bloom.  The '/' to '_'
conversion exists just to make sure our new file remains in the same
directory as where the conflict that caused us to need a new unique
path occurred.

But unique_path() does NOT end immediately after calling
add_flattened_path() and there is no collision possible in the return
from unique_path(), because it ends with a
    while (strmap_contains(existing_paths, newpath.buf)) {
loop that modifies the resulting path until it finds one that doesn't
collide with an existing path.

  reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-18  5:51 [PATCH 00/10] merge-ort: add more handling of basic conflict types Elijah Newren via GitGitGadget
2020-12-18  5:51 ` [PATCH 01/10] merge-ort: handle D/F conflict where directory disappears due to merge Elijah Newren via GitGitGadget
2020-12-30 14:06   ` Derrick Stolee
2020-12-30 15:13     ` Elijah Newren
2020-12-31 11:17       ` Derrick Stolee
2020-12-31 17:13         ` Elijah Newren
2020-12-18  5:51 ` [PATCH 02/10] merge-ort: handle directory/file conflicts that remain Elijah Newren via GitGitGadget
2020-12-18  5:51 ` [PATCH 03/10] merge-ort: implement unique_path() helper Elijah Newren via GitGitGadget
2020-12-30 14:16   ` Derrick Stolee
2020-12-30 15:10     ` Elijah Newren [this message]
2020-12-31 11:19       ` Derrick Stolee
2020-12-18  5:51 ` [PATCH 04/10] merge-ort: handle book-keeping around two- and three-way content merge Elijah Newren via GitGitGadget
2020-12-18  5:51 ` [PATCH 05/10] merge-ort: flesh out implementation of handle_content_merge() Elijah Newren via GitGitGadget
2020-12-18  5:51 ` [PATCH 06/10] merge-ort: copy and adapt merge_3way() from merge-recursive.c Elijah Newren via GitGitGadget
2020-12-18  5:51 ` [PATCH 07/10] merge-ort: copy and adapt merge_submodule() " Elijah Newren via GitGitGadget
2020-12-18  5:51 ` [PATCH 08/10] merge-ort: implement format_commit() Elijah Newren via GitGitGadget
2020-12-18  5:51 ` [PATCH 09/10] merge-ort: copy find_first_merges() implementation from merge-recursive.c Elijah Newren via GitGitGadget
2020-12-18  5:51 ` [PATCH 10/10] merge-ort: add handling for different types of files at same path Elijah Newren via GitGitGadget
2020-12-29  0:44 ` [PATCH 00/10] merge-ort: add more handling of basic conflict types Elijah Newren
2021-01-01  2:34 ` [PATCH v2 " Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 01/10] merge-ort: handle D/F conflict where directory disappears due to merge Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 02/10] merge-ort: handle directory/file conflicts that remain Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 03/10] merge-ort: implement unique_path() helper Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 04/10] merge-ort: handle book-keeping around two- and three-way content merge Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 05/10] merge-ort: flesh out implementation of handle_content_merge() Elijah Newren via GitGitGadget
2021-03-04 16:28     ` A merge-ort TODO comment, and how to test merge-ort? Ævar Arnfjörð Bjarmason
2021-03-04 19:43       ` Elijah Newren
2021-03-04 21:29         ` Ævar Arnfjörð Bjarmason
2021-03-04 22:45           ` Elijah Newren
2021-03-08 14:49             ` Ævar Arnfjörð Bjarmason
2021-01-01  2:34   ` [PATCH v2 06/10] merge-ort: copy and adapt merge_3way() from merge-recursive.c Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 07/10] merge-ort: copy and adapt merge_submodule() " Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 08/10] merge-ort: implement format_commit() Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 09/10] merge-ort: copy find_first_merges() implementation from merge-recursive.c Elijah Newren via GitGitGadget
2021-01-01  2:34   ` [PATCH v2 10/10] merge-ort: add handling for different types of files at same path Elijah Newren via GitGitGadget
2021-01-05 14:23   ` [PATCH v2 00/10] merge-ort: add more handling of basic conflict types Derrick Stolee
2021-01-06 19:20     ` Elijah Newren

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