From: Elijah Newren <email@example.com> To: Jonathan Tan <firstname.lastname@example.org> Cc: Git Mailing List <email@example.com> Subject: Re: [PATCH v2 08/20] merge-ort: compute a few more useful fields for collect_merge_info Date: Mon, 9 Nov 2020 15:05:48 -0800 Message-ID: <CABPp-BFNk5ZQLyo5G-7vq3XD3s6z_rGUNM3QL14hXvMYTzK_Ug@mail.gmail.com> (raw) In-Reply-To: <firstname.lastname@example.org> On Mon, Nov 9, 2020 at 2:04 PM Jonathan Tan <email@example.com> wrote: > > > On Fri, Nov 6, 2020 at 2:52 PM Jonathan Tan <firstname.lastname@example.org> wrote: > > > > > > > + /* > > > > + * Note: We only label files with df_conflict, not directories. > > > > + * Since directories stay where they are, and files move out of the > > > > + * way to make room for a directory, we don't care if there was a > > > > + * directory/file conflict for a parent directory of the current path. > > > > + */ > > > > + unsigned df_conflict = (filemask != 0) && (dirmask != 0); > > > > > > Suppose you have: > > > > > > [ours] > > > foo/ > > > bar/ > > > baz > > > quux > > > [theirs] > > > foo > > > > > > By "we only label files with df_conflict, not directories", are you > > > referring to not labelling "foo/" in [ours], or to "bar/", "baz", and > > > "quux" (so, the files and directories within a directory)? At first I > > > thought you were referring to the former, but perhaps you are referring > > > to the latter. > > > > The former. I was drawing a distinction between how this code > > operates, and how unpack_trees() operates, which probably only matters > > to those familiar with unpack_trees() or who have been reading through > > it recently. > > Just for clarification: do you mean "the latter"? (The "not" in my > question might be confusing.) Yeah, probably was confusing, so let me just state where you are almost right below. > To be more illustrative in what I meant, at first I thought that you > were NOT labelling "foo/" in [ours], hence: > > [ours] > foo/ <- unlabeled > [theirs] > foo <- labeled > > In this way, in a sense, you are indeed labelling only the file, not the > directory. > > But instead what you seem to be doing is this: > > [ours] > foo/ <- labeled > bar/ <- unlabeled > baz <- unlabeled > quux <- unlabeled > [theirs] > foo <- labeled > > which is what I meant by NOT labelling "bar/", "baz", and "quux". I'm doing something /really/ close to this, yes. However, just to be pedantic, there is no "foo/". '/' is an illegal character in a filename to record in a tree. One side has a "foo" whose mode and object_id happen to reflect a tree rather than a blob. But I only have one conflict_info per pathname, not 3 (can't have three since strmaps don't allow duplicate keys, and wouldn't want it if I could). That one conflict_info stores 3 (mode, object_id) pairs, and also has a single df_conflict bit. So, I label "foo" by setting that df_conflict bit. But I only pay attention to it for the pairs representing a blob, not the ones representing a tree. And I don't propagate the information down to paths below the foo directory. > > unpack_trees() will note when there is a directory/file > > conflict, and propagates that information to all subtrees, with every > > path specially checking for the o->df_conflict_entry and then handling > > it specially (e.g. keeping higher order stages instead of using an > > aggressive or trivial resolutions). > > And here it seems like you're describing that unpack_trees() would label > it in this way: > > [ours] > foo/ <- labeled > bar/ <- labeled > baz <- labeled > quux <- labeled > [theirs] > foo <- labeled > > (and you're emphasizing by contrast that merge-ort is NOT doing this). Correct. > > However, leaving both a file and > > a directory at the same path, while allowed in the index, makes for > > ugliness and difficulty for users to resolve. Plus it isn't allowed > > in the working tree anyway. We decided a while ago that it'd be > > better to represent these conflicts differently, . > > > > Also, at the time you are unpacking or traversing trees, you only know > > if one side had a directory where the other side had a file. You > > don't know if the final merge result will actually have a > > directory/file conflict. If the file existed in both the base version > > and unmodified on one side, for example, then the file will be removed > > as part of the merge. It is similarly possible that the entire > > directory of files all need to be deleted or are all renamed > > elsewhere. So, you have to keep track of a df_conflict bit, but you > > can't act on it until you've processed several other things first. > > > > Since I already know I'm not going to move a whole directory of files > > out of the way so that a file can be placed in the working tree > > instead of that whole directory, the directory doesn't need to be > > tweaked. I'm not going to propagate any information about a > > directory/file conflict at some path down to all subpaths of the > > directory. I only track it for the file that immediately conflicts, > > and then only take action on it after resolving all the paths under > > the corresponding directory to see if the directory/file conflict > > remains. > > > >  https://email@example.com/ > > and the thread surrounding it > >  https://firstname.lastname@example.org/, > > which is now commit ef52778708 ("merge tests: expect improved > > directory/file conflict handling in ort", 2020-10-26) > > Makes sense. > > > > > @@ -161,6 +179,13 @@ static int collect_merge_info_callback(int n, > > > > newinfo.name = p->path; > > > > newinfo.namelen = p->pathlen; > > > > newinfo.pathlen = st_add3(newinfo.pathlen, p->pathlen, 1); > > > > + /* > > > > + * If we did care about parent directories having a D/F > > > > + * conflict, then we'd include > > > > + * newinfo.df_conflicts |= (mask & ~dirmask); > > > > + * here. But we don't. (See comment near setting of local > > > > + * df_conflict variable near the beginning of this function). > > > > + */ > > > > > > I'm not sure how "mask" and "dirmask" contains information about parent > > > directories. "mask" represents the available entries, and "dirmask" > > > represents which of them are directories, as far as I know. So we can > > > notice when something is missing, but I don't see how this distinguishes > > > between the case that something is missing because it was in a parent > > > directory that got deleted, vs something is missing because it itself > > > got deleted. > > > > Yeah, this is more comparisons to unpack_trees. This code is about to > > set up a recursive call into subdirectories. newinfo is set based on > > the mask and dirmask of the current entry, and then subdirectories can > > consult newinfo.df_conflicts to see if that path is within a directory > > that was involved in a directory/file conflict. For example: > > > > Tree in base version: > > foo/ > > bar > > stuff.txt > > Tree on side 1: (adds foo/baz) > > foo/ > > bar > > baz > > stuff.txt > > Tree on side 2: (deletes foo/, adds new file foo) > > foo > > stuff.txt > > > > When processing 'foo', we have mask=7, dirmask = 3. So, here > > unpack_trees() would have set newinfo.df_conflicts = (mask & ~dirmask) > > = 4. Then when we process foo/bar or foo/baz, we have mask=2, > > dirmask=0, which looks like there are no directory/file conflicts. > > However, we can note that these paths are under a directory involved > > in a directory/file conflict via info.df_conflicts whose value is 4. > > unpack_trees() cared about paths under a directory that was involved > > in a directory/file conflict, and someone familiar with that code > > might ask why I don't also track the same information. The answer is > > that I don't track it, even though I thought about it, because it's > > useless overhead since I'm going to leave the directory alone and move > > the file out of the way. > > > > Does that make sense? > > Ah...yes, that makes sense. I think I didn't notice the "newinfo", so I > didn't realize that we were setting the info of our children based on > ourselves. Perhaps I would have noticed it sooner if the comment had > read "If this file/directory cared about its parent directory (the > current directory) having a D/F conflict, then we'd propagate the masks > in this way:" instead of "If we did care about parent directories having > a D/F conflict", but perhaps the point is already obvious enough. I'm happy to reword it if that makes it clearer. Thanks for the suggestion.
next prev parent reply index Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-02 20:43 [PATCH v2 00/20] fundamentals of merge-ort implementation Elijah Newren 2020-11-02 20:43 ` [PATCH v2 01/20] merge-ort: setup basic internal data structures Elijah Newren 2020-11-06 22:05 ` Jonathan Tan 2020-11-06 22:45 ` Elijah Newren 2020-11-09 20:55 ` Jonathan Tan 2020-11-02 20:43 ` [PATCH v2 02/20] merge-ort: add some high-level algorithm structure Elijah Newren 2020-11-02 20:43 ` [PATCH v2 03/20] merge-ort: port merge_start() from merge-recursive Elijah Newren 2020-11-11 13:52 ` Derrick Stolee 2020-11-11 16:22 ` Elijah Newren 2020-11-02 20:43 ` [PATCH v2 04/20] merge-ort: use histogram diff Elijah Newren 2020-11-11 13:54 ` Derrick Stolee 2020-11-11 16:47 ` Elijah Newren 2020-11-11 16:51 ` Derrick Stolee 2020-11-11 17:03 ` Elijah Newren 2020-11-02 20:43 ` [PATCH v2 05/20] merge-ort: add an err() function similar to one from merge-recursive Elijah Newren 2020-11-11 13:58 ` Derrick Stolee 2020-11-11 17:07 ` Elijah Newren 2020-11-11 17:10 ` Derrick Stolee 2020-11-02 20:43 ` [PATCH v2 06/20] merge-ort: implement a very basic collect_merge_info() Elijah Newren 2020-11-06 22:19 ` Jonathan Tan 2020-11-06 23:10 ` Elijah Newren 2020-11-09 20:59 ` Jonathan Tan 2020-11-11 14:38 ` Derrick Stolee 2020-11-11 17:02 ` Elijah Newren 2020-11-02 20:43 ` [PATCH v2 07/20] merge-ort: avoid repeating fill_tree_descriptor() on the same tree Elijah Newren 2020-11-11 14:51 ` Derrick Stolee 2020-11-11 17:13 ` Elijah Newren 2020-11-11 17:21 ` Eric Sunshine 2020-11-02 20:43 ` [PATCH v2 08/20] merge-ort: compute a few more useful fields for collect_merge_info Elijah Newren 2020-11-06 22:52 ` Jonathan Tan 2020-11-06 23:41 ` Elijah Newren 2020-11-09 22:04 ` Jonathan Tan 2020-11-09 23:05 ` Elijah Newren [this message] 2020-11-02 20:43 ` [PATCH v2 09/20] merge-ort: record stage and auxiliary info for every path Elijah Newren 2020-11-06 22:58 ` Jonathan Tan 2020-11-07 0:26 ` Elijah Newren 2020-11-09 22:09 ` Jonathan Tan 2020-11-09 23:08 ` Elijah Newren 2020-11-11 15:26 ` Derrick Stolee 2020-11-11 18:16 ` Elijah Newren 2020-11-11 22:06 ` Elijah Newren 2020-11-12 18:23 ` Derrick Stolee 2020-11-12 18:39 ` Derrick Stolee 2020-11-02 20:43 ` [PATCH v2 10/20] merge-ort: avoid recursing into identical trees Elijah Newren 2020-11-11 15:31 ` Derrick Stolee 2020-11-02 20:43 ` [PATCH v2 11/20] merge-ort: add a preliminary simple process_entries() implementation Elijah Newren 2020-11-11 19:51 ` Jonathan Tan 2020-11-12 1:48 ` Elijah Newren 2020-11-02 20:43 ` [PATCH v2 12/20] merge-ort: have process_entries operate in a defined order Elijah Newren 2020-11-11 16:09 ` Derrick Stolee 2020-11-11 18:58 ` Elijah Newren 2020-11-02 20:43 ` [PATCH v2 13/20] merge-ort: step 1 of tree writing -- record basenames, modes, and oids Elijah Newren 2020-11-11 20:01 ` Jonathan Tan 2020-11-11 20:24 ` Elijah Newren 2020-11-12 20:39 ` Jonathan Tan 2020-11-02 20:43 ` [PATCH v2 14/20] merge-ort: step 2 of tree writing -- function to create tree object Elijah Newren 2020-11-11 20:47 ` Jonathan Tan 2020-11-11 21:21 ` Elijah Newren 2020-11-02 20:43 ` [PATCH v2 15/20] merge-ort: step 3 of tree writing -- handling subdirectories as we go Elijah Newren 2020-11-12 20:15 ` Jonathan Tan 2020-11-12 22:30 ` Elijah Newren 2020-11-24 20:19 ` Elijah Newren 2020-11-25 2:07 ` Jonathan Tan 2020-11-26 18:13 ` Elijah Newren 2020-11-30 18:41 ` Jonathan Tan 2020-11-02 20:43 ` [PATCH v2 16/20] merge-ort: basic outline for merge_switch_to_result() Elijah Newren 2020-11-02 20:43 ` [PATCH v2 17/20] merge-ort: add implementation of checkout() Elijah Newren 2020-11-02 20:43 ` [PATCH v2 18/20] tree: enable cmp_cache_name_compare() to be used elsewhere Elijah Newren 2020-11-02 20:43 ` [PATCH v2 19/20] merge-ort: add implementation of record_unmerged_index_entries() Elijah Newren 2020-11-02 20:43 ` [PATCH v2 20/20] merge-ort: free data structures in merge_finalize() Elijah Newren 2020-11-03 14:49 ` [PATCH v2 00/20] fundamentals of merge-ort implementation Derrick Stolee 2020-11-03 16:36 ` Elijah Newren 2020-11-07 6:06 ` Elijah Newren 2020-11-07 15:02 ` Derrick Stolee 2020-11-07 19:39 ` Elijah Newren 2020-11-09 12:30 ` Derrick Stolee 2020-11-09 17:13 ` Elijah Newren 2020-11-09 19:51 ` Derrick Stolee 2020-11-09 22:44 ` Elijah Newren 2020-11-11 17:08 ` Derrick Stolee 2020-11-11 18:35 ` Elijah Newren 2020-11-11 20:48 ` Derrick Stolee 2020-11-11 21:18 ` Elijah Newren 2020-11-29 7:43 [PATCH " Elijah Newren via GitGitGadget 2020-12-04 20:47 ` [PATCH v2 " Elijah Newren via GitGitGadget 2020-12-04 20:47 ` [PATCH v2 08/20] merge-ort: compute a few more useful fields for collect_merge_info Elijah Newren via GitGitGadget
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=CABPp-BFNk5ZQLyo5G-7vq3XD3s6z_rGUNM3QL14hXvMYTzK_Ug@mail.gmail.com \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
Git Mailing List Archive on lore.kernel.org Archives are clonable: git clone --mirror https://lore.kernel.org/git/0 git/git/0.git # If you have public-inbox 1.1+ installed, you may # initialize and index your mirror using the following commands: public-inbox-init -V2 git git/ https://lore.kernel.org/git \ firstname.lastname@example.org public-inbox-index git Example config snippet for mirrors Newsgroup available over NNTP: nntp://nntp.lore.kernel.org/org.kernel.vger.git AGPL code for this site: git clone https://public-inbox.org/public-inbox.git