Very good explanation. It clarifies something. I read some comments about
using "subtree" vs "submodules". In most places people give a bad score to
Четвер, 25 вересня 2014 р. 17:05:21 UTC+3 користувач Konstantin Khomoutov
> On Thu, 25 Sep 2014 04:28:16 -0700 (PDT)
> > > you have to turn each of these directories into separate
> > > repositories and either use the so-called "subtree merging" or
> > > submodules.
> > I was going to do so. Maybe it was not clear from my scheme in
> > original question. I edited it to clarify.
> > Proj1_2_common/
> > .git/
> > ...
> > Proj1_2_3_common/
> > .git/
> > ...
> > Proj1/
> > .git/
> > And after this again: what is advantages of "subtree" or "submodules"
> > over just add "Proj1_2_common/" to project in IDE and use it repo
> > separately?
> Ah, I see now, thanks.
> The problem with simply adding them all into an IDE project is that
> tracking that project's history with Git (I mean, tracking the files
> comprising what constitutes a project in your IDE, such as .sln and a
> set of *.csproj files for an C#/.NET application, and may be also some
> code files etc) will produce a series of commits which, themselves,
> contain no record of which exact states all of the referenced
> subprojects were in when that commit has been recorded.
> Let me try to explain that in more words.
> Suppose you did what you intended, and just slapped a bunch of
> git-clone'd projects under a single directory, and added references
> to the files in them to your IDE's project. So far so good.
> Now some time passes and some of those referenced projects get updated.
> You'll typically `cd` into each of the referenced projects and do
> `git pull` (or may be something more appropriate) there -- to bring the
> latest changes in. You will then possibly make some adjustments to your
> "superproject" and commit these changes.
> Now you see that should you have the need to check out some *past*
> revision of your superproject (maybe during `git bisect` or to just
> fork a branch off some prior state etc), you'll discover that the
> commit you're about to check out has no idea about which precise states
> of the subprojects it references have been checked out when that commit
> has been recorded. That happens because the synthetic state of all the
> checked out projects was "ad hoc", and was never recorded anywhere,
> Enter subtree merging or submodules.
> With subtree merging, you have histories of subprojects recorded in
> your repository. You merge (and later re-merge) their new state
> into your superproject from time to time, and hence any commit you
> record "on the top level" -- for the files comprising the superproject
> itself -- automatically references the correct states of all the
> subprojects -- because they're in the same repository.
> With submodules, your superproject maintains a list of submodules,
> and each commit recorded in the superproject records SHA-1 names
> of the commits currently checked out in each submodule at the time
> the commit is created.
> Hence, with either approach, when you later check any of your past
> revisions of the superproject, the exact state of the whole thing is
> Pros and cons of these approaches are:
> Subtree merging has everything in the single repository:
> easier to carry around and view the history.
> But this comes at the cost of having the histories
> of the subproject in the superproject's repository.
> Submodules require accessing other repos when you clone
> the superproject and hence the superproject's repo is not
> free-standing. On the other hand, there is no history duplication.
> > And what about history of old and new repos?
> Either approach will make histories of subprojects available
> when working on the superproject, though via different means.
> Of course, you will have a single point in the history of your
> superproject where you will have started using either of the
> approaches explained above. If you want to somehow retrofit past
> states of the subproject's histories intertwined with certain past
> states of the superproject this is another task completely and,
> while supposedly doable, this will be hard and tedious and manual
> to get done.
> > it still would be better if you have copied the original answer inline
> > Only answer without question?
> My bad: I meant question.
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