On Tue, Mar 27, 2018 at 5:17 PM, Stefan Beller <sbel...@google.com> wrote: >> >> $ git diff --submodule=log --submodule-log-detail=(long|short) >> >> >> >> I'm not sure what makes sense here. I welcome thoughts/discussion and >> >> will provide follow-up patches. >> > >> > The case of merges is usually configured with --[no-]merges, or >> > --min-parents=<n>. > >> But that is a knob that controls an irrelevant aspect of the detail >> in the context of this discussion, isn't it? This code is about "to >> what degree the things that happened between two submodule commits >> in an adjacent pair of commits in the superproject are summarized?" > > And I took it a step further and wanted to give a general solution, which > allows giving any option that the diff machinery accepts to only apply > to the submodule diffing part of the current diff. > >> The hack Robert illustrates below is to change it to stop favouring >> such projects with "clean" histories, and show "log --oneline >> --no-merges --left-right". When presented that way, clean histories >> of topic-branch based projects will suffer by losing conciseness, >> but clean histories of totally linear projects will still be shown >> the same way, and messy history that sometimes merges, sometimes >> merges mergy histories, and sometimes directly builds on the trunk >> will be shown as an enumeration of individual commits in a flat way >> by ignoring merges and not restricting the traversal to the first >> parent chains, which would appear more uniform than what the current >> code shows. > > Oh, I realize this is in the *summary* code path, I was thinking about the > show_submodule_inline_diff, which would benefit from more diff options. > >> I do not see a point in introducing --min/max-parents as a knob to >> control how the history is summarized. > > For a summary a flat list of commits may be fine, ignoring > (ideally non-evil) merges. > >> This is a strongly related tangent, but I wonder if we can and/or >> want to share more code with the codepath that prepares the log >> message for a merge. It summarizes what happened on the side branch >> since it forked from the history it is joining back to (I think it >> is merge.c::shortlog() that computes this) > > I do not find code there. To me it looks like builtin/fmt-merge-msg.c > is responsible for coming up with a default merge message? > In that file there is a shortlog() function, which walks revisions > and puts together the subject lines of commits. > >> and it is quite similar >> to what Robert wants to use for submodules here. On the other hand, >> in a project _without_ submodule, if you are pulling history made by >> your lieutenant whose history is full of linear merges of topic >> branches to the mainline, it may not be a bad idea to allow >> fmt-merge-msg to alternatively show something similar to the "diff >> --submodule=log" gives us, i.e. summarize the history of the side >> branch being merged by just listing the commits on the first-parent >> chain. So I sense some opportunity for cross pollination here. > > The cross pollination that I sense is the desire in both cases to freely > specify the format as it may depend on the workflow.
First I want to apologize for having taken so long to get back with each of you about this. I actually have a lot of work started to expand the --submodule option to add a "full-log" option in addition to the existing "log". This is a pretty big task for me already, mostly because I'm unfamiliar with git and have limited personal time to do this at home (this is part of what I am apologizing for). I kind of get what Stefan and Junio are saying. There's a lot of opportunity for cleanup. More specific to my use case, adding some functionality to generate a log message (although I've developed a bash script to do this since I wrote my original email. I'll attach it to this email for those interested). Also I get that taking this a notch higher and adding a new option to pass options down to submodules also addresses my case. Before I waste anyone's time on this, I want to make sure that my very narrow and specific implementation will be ideal. By all means I do not want to do things the easy way which ends up adding "cruft" you'll have to deal with later. If there's a larger effort to generalize this and other things related to submodules maybe I can just wait for that to happen instead? What direction would you guys recommend? Junio basically hit the nail on the head with the comparisons of different mainlines. I think some repositories are more disciplined than others. At my workplace, I deal with a lot of folks that aren't interested in learning git beyond the required day to day responsibilities. It's difficult to enforce very specific branching, rebase, and merge habits. As such, the best I can do to work around that for building release notes is to exclude merge commits (since most of the time, people keep the default message which is generally useless) and include all commits in the ancestry path (since often times commits on the right side of a merge will have important information such as JIRA issue keys, which if shown in the parent repo will cause appropriate links back to parent repositories to show when changes in submodules were introduced there as well). Based on how constructive this email thread has gotten since I started it, I'm starting to feel like my solution is too narrowly-focused and doesn't have the long term appeal expected. Let me know, I'm happy to do what I can but I think it will be limited due to my lack of domain expertise in the code base and inability to invest the required time for significant scope of work.
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