Hi Junio,
On Fri, 7 Nov 2014, Junio C Hamano wrote:
> Johannes Schindelin <johannes.schinde...@gmx.de> writes:
>
> > Under certain circumstances, it makes a *lot* of sense to allow pushing
> > into the current branch. For example, when two machines with different
> > Operating Systems are required for testing, it makes much more sense to
> > synchronize between working directories than having to go via a third
> > server.
>
> Even if you do not have a third server, each time you decide to do
> such a push, you have a single source of truth, i.e. the repository
> you are pushing from, so instead of doing that push, all the others
> could instead pull from that single source of truth. In that sense,
> even though I wouldn't say it is wrong to use "push" in the opposite
> direction for this synchronization, I have to say that the above is
> not a very strong argument. It certainly does not deserve "*lot*"
> in bold font ;-)
I am sorry, I should have been more explicit about the fact that other
"Operating System" includes also Windows, where it is a major hassle to
set up an ssh daemon, hence the asymmetry of ease to connect from one to
another machine. I really thought that was obvious, my apologies. My next
patch iteration will have the Windows scenario as motivation.
Note that I did not even dive into the problem of many loaner laptops
where you are not allowed to set up an ssh daemon, or even know the
user's password. I did not mention those problems because I again assumed
(again, apologies) that this was obvious because it occurred to me
automatically when thinking about the multi-laptop problem.
And I must apologize yet again, for I also failed to specify explicitly
another reason why pushing makes a *lot* more sense than pulling: at least
for me, personally, having to switch keyboards just to synchronize Git
checkouts from one to another computer *is* a hassle.
> > Under different circumstances, the working directory needs to be left
> > untouched, for example when a bunch of VMs need to be shut down to save
> > RAM and one needs to push everything out into the host's non-bare
> > repositories quickly.
>
> For this use case, if you assume that the tips of branches in the
> repositories on "a bunch of VMs" could be pointing at different
> commits (i.e. each of them has acquired more work without
> coordination), you are risking lossage by pushing into refs/heads/,
> not refs/remotes/vm$n/, aren't you? When you want to save things
> away "quickly", you do not want to be worried about a push from VM1
> stomping on what was stored from VM0, and using separate remotes,
> i.e. refs/remotes/vm$n/, has been the recommended way to do so. So
> this is not a very strong argument, either.
I thank you for your assessment of my personal working style.
:-)
And yet again I have to apologize because I find that relying on Git's
fast-forward default (you need to force non-fast-forward ref updates,
which I don't, at least not by default) saves me from that lossage, and
will therefore not change my personal working style that served me so well
for years.
> I do not think of a good justification of detachInstead offhand, but
> you must have thought things through a lot more than I did, so you
> can come up with a work flow description that is more usable by mere
> mortals to justify that mode.
The main justification is that it is safer than updateInstead because it
is guaranteed not to modify the working directory. I intended it for use
by developers who are uncomfortable with updating the working directory
through a push, and as uncomfortable with forgetting about temporary
branches pushed, say, via "git push other-computer HEAD:refs/heads/tmp".
However, I have to admit that I never used this myself after the first few
weeks of playing with this patch series.
> Without such a description to justify why detachInstead makes sense, for
> example, I cannot even answer this simple question:
>
> Would it make sense to have a third mode, "check out if the
> working tree is clean, detach otherwise"?
I imagine that some developer might find that useful. If you insist, I
will implement it, even if I personally deem this mode way too complicated
a concept for myself to be used safely.
> > [... snip a lot of text that made me almost miss the comments below ...]
> >
> > diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
> > index 32fc540..be4172f 100644
> > --- a/builtin/receive-pack.c
> > +++ b/builtin/receive-pack.c
> > @@ -26,7 +26,9 @@ enum deny_action {
> > DENY_UNCONFIGURED,
> > DENY_IGNORE,
> > DENY_WARN,
> > - DENY_REFUSE
> > + DENY_REFUSE,
> > + DENY_UPDATE_INSTEAD,
> > + DENY_DETACH_INSTEAD,
>
> Don't add trailing comma after the last element of enum.
Will fix in the next iteration.
> > @@ -730,6 +737,44 @@ static int update_shallow_ref(struct command *cmd,
> > struct shallow_info *si)
> > return 0;
> > }
> >
> > +static void merge_worktree(unsigned char *sha1)
> > +{
> > + const char *update_refresh[] = {
> > + "update-index", "--refresh", NULL
> > + };
> > + const char *read_tree[] = {
> > + "read-tree", "-u", "-m", sha1_to_hex(sha1), NULL
> > + };
> > + struct child_process child;
> > + struct strbuf git_env = STRBUF_INIT;
> > + const char *env[2];
> > +
> > + if (is_bare_repository())
> > + die ("denyCurrentBranch = updateInstead needs a worktree");
>
> Why have extra SP only after "die" but not other function names?
Will remove the space in the next iteration.
> > + strbuf_addf(&git_env, "GIT_DIR=%s", absolute_path(get_git_dir()));
> > + env[0] = git_env.buf;
> > + env[1] = NULL;
>
> Doesn't child.env have managed argv_array these days?
I missed those developments, likewise the introduction of
CHILD_PROCESS_INIT. Fixed in the next iteration.
> > + memset(&child, 0, sizeof(child));
> > + child.argv = update_refresh;
> > + child.env = env;
> > + child.dir = git_work_tree_cfg ? git_work_tree_cfg : "..";
> > + child.stdout_to_stderr = 1;
> > + child.git_cmd = 1;
> > + if (run_command(&child))
> > + die ("Could not refresh the index");
> > +
> > + child.argv = read_tree;
> > + child.no_stdin = 1;
> > + child.no_stdout = 1;
> > + child.stdout_to_stderr = 0;
> > + if (run_command(&child))
> > + die ("Could not merge working tree with new HEAD. Good luck.");
>
> Drop "Good luck." and replace it with a more useful info. At least,
> tell the user what state you left her repository in by this botched
> attempt, so that she can manually recover.
The best information Git can give at that point is that the working tree
could not be merged with the new HEAD. I stripped "Good luck." in the next
iteration, although I mourn the loss of comedy in Git.
Ciao,
Johannes
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