* `git fetch` not updating 'origin/HEAD' after branch rename @ 2021-04-13 20:25 Sam Bostock 2021-04-13 20:37 ` Junio C Hamano 2021-04-14 0:26 ` Chris Torek 0 siblings, 2 replies; 10+ messages in thread From: Sam Bostock @ 2021-04-13 20:25 UTC (permalink / raw) To: git Hi! Hopefully I followed the instructions on https://git-scm.com/community correctly to report this bug. Long story short, it seems to me that `git fetch` should update "refs/remotes/origin/HEAD" when the upstream HEAD changes, but it doesn't. See my filled out bug report below. Thanks, Sam ---- Thank you for filling out a Git bug report! Please answer the following questions to help us understand your issue. What did you do before the bug happened? (Steps to reproduce your issue) 1. Clone a repo with some branch name (say "master") from some remote origin (say GitHub). 2. Replace/rename the main branch on the remote (say "main"). 3. Run `git fetch` locally to sync with remote. 4. Run `git rev-parse --abbrev-ref --verify origin/HEAD`. What did you expect to happen? (Expected behavior) The `git fetch` should update the refs accordingly so "origin/HEAD" now points to the new branch, which should be output from the command above: $ git rev-parse --abbrev-ref --verify origin/HEAD origin/main What happened instead? (Actual behavior) The "origin/HEAD" ref seems to not point to anything anymore (because the branch it was pointing to was "deleted"). `git fetch` fails to update it to reflect the change. $ git rev-parse --abbrev-ref --verify origin/HEAD fatal: Needed a single revision What's different between what you expected and what actually happened? The HEAD on origin has changed, but this change is not reflected in the local refs by `git fetch`. Anything else you want to add: Please review the rest of the bug report below. You can delete any lines you don't wish to share. [System Info] git version: git version 2.30.2 cpu: x86_64 no commit associated with this build sizeof-long: 8 sizeof-size_t: 8 shell-path: /nix/store/74shlfgb18717ixjlpivpxd7iqcyhyn5-bash-4.4-p23/bin/bash uname: Darwin 19.6.0 Darwin Kernel Version 19.6.0: Tue Jan 12 22:13:05 PST 2021; root:xnu-6153.141.16~1/RELEASE_X86_64 x86_64 compiler info: clang: 7.1.0 (tags/RELEASE_710/final) libc info: no libc information available $SHELL (typically, interactive shell): /usr/local/bin/bash [Enabled Hooks] ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-13 20:25 `git fetch` not updating 'origin/HEAD' after branch rename Sam Bostock @ 2021-04-13 20:37 ` Junio C Hamano 2021-04-13 21:09 ` Andreas Schwab 2021-04-14 0:26 ` Chris Torek 1 sibling, 1 reply; 10+ messages in thread From: Junio C Hamano @ 2021-04-13 20:37 UTC (permalink / raw) To: Sam Bostock; +Cc: git Sam Bostock <sam.bostock@shopify.com> writes: > Hopefully I followed the instructions on https://git-scm.com/community > correctly to report this bug. > > Long story short, it seems to me that `git fetch` should update > "refs/remotes/origin/HEAD" when the upstream HEAD changes, but it > doesn't. See my filled out bug report below. That is working as intended. Since its inception, refs/remotes/origin/HEAD has been designed to mean "the branch, which the owner of the repository considers the most interesting for his/her purpose to keep track in the 'origin' remote repository". It is perfectly OK to repoint origin/HEAD to point at another branch you are interested in after you make a clone. The origin/HEAD happens to be primed by noticing what the remote repository sets HEAD to point to their branch upon cloning, but that is purely for convenience (i.e. HEAD branch of a repository offered for cloning points at a branch the owner of the repository being cloned considers the primary branch in his/her repository, and that often coincides with the earlier definition of origin/HEAD for those who clone such a repository). It would be a bug to update it to something other than you set (either passively by keeping what "clone" gave you initially, or actively by updating it to point at another branch) upon "git fetch" from the remote. There was an idea floated to use the same mechanism used by "git clone" to prime origin/HEAD upon "git fetch" when origin/HEAD is missing, and I do not think there were many objections against the idea, so that may happen sometime in the future. It may also be possible to add "git fetch --reset-remote-tracking-HEAD" option to make "fetch" overwrite existing origin/HEAD but somebody has to propose such a change, argue for its benefit and get it accepted by the community. Thanks. ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-13 20:37 ` Junio C Hamano @ 2021-04-13 21:09 ` Andreas Schwab 2021-04-13 21:22 ` Junio C Hamano 0 siblings, 1 reply; 10+ messages in thread From: Andreas Schwab @ 2021-04-13 21:09 UTC (permalink / raw) To: Junio C Hamano; +Cc: Sam Bostock, git On Apr 13 2021, Junio C Hamano wrote: > It may also be > possible to add "git fetch --reset-remote-tracking-HEAD" option to > make "fetch" overwrite existing origin/HEAD but somebody has to > propose such a change, argue for its benefit and get it accepted by > the community. Isn't that what git remote set-head origin -a does? Andreas. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1 "And now for something completely different." ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-13 21:09 ` Andreas Schwab @ 2021-04-13 21:22 ` Junio C Hamano 0 siblings, 0 replies; 10+ messages in thread From: Junio C Hamano @ 2021-04-13 21:22 UTC (permalink / raw) To: Andreas Schwab; +Cc: Sam Bostock, git Andreas Schwab <schwab@linux-m68k.org> writes: > On Apr 13 2021, Junio C Hamano wrote: > >> It may also be >> possible to add "git fetch --reset-remote-tracking-HEAD" option to >> make "fetch" overwrite existing origin/HEAD but somebody has to >> propose such a change, argue for its benefit and get it accepted by >> the community. > > Isn't that what git remote set-head origin -a does? Yes, but the point is to do so when fetch is run (i.e. it talks with the other side not just to learn which branch their HEAD points at, but it actually does the fetching of new history on branches). And it might open the door to add a configuration to tell "fetch" to do so unconditionally, if it turns out to be useful enough. ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-13 20:25 `git fetch` not updating 'origin/HEAD' after branch rename Sam Bostock 2021-04-13 20:37 ` Junio C Hamano @ 2021-04-14 0:26 ` Chris Torek 2021-04-14 5:29 ` Jeff King 2021-04-14 10:56 ` Ævar Arnfjörð Bjarmason 1 sibling, 2 replies; 10+ messages in thread From: Chris Torek @ 2021-04-14 0:26 UTC (permalink / raw) To: Sam Bostock; +Cc: Git List On Tue, Apr 13, 2021 at 5:18 PM Sam Bostock <sam.bostock@shopify.com> wrote: > Long story short, it seems to me that `git fetch` should update > "refs/remotes/origin/HEAD" when the upstream HEAD changes, but it > doesn't. It's never been the *intent* to have `git fetch` update the corresponding remote-tracking `HEAD` ref. To make that happen, you must run `git remote`: git remote set-head origin -a for instance. I have, however, often thought that this is the wrong *default* way for things to work, and that at least by default, `git fetch origin` should update `origin/HEAD` if the fetch result indicates that it should. See also Junio's reply. I think a configuration knob (similar to `fetch.prune`) would be reasonable here. Users could then be encouraged to set `fetch.prune` to `true`, and `fetch.update-remote-HEAD` (or whatever) to `true` as well. Chris ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-14 0:26 ` Chris Torek @ 2021-04-14 5:29 ` Jeff King 2021-04-14 10:56 ` Ævar Arnfjörð Bjarmason 1 sibling, 0 replies; 10+ messages in thread From: Jeff King @ 2021-04-14 5:29 UTC (permalink / raw) To: Chris Torek; +Cc: Junio C Hamano, Sam Bostock, Git List On Tue, Apr 13, 2021 at 05:26:02PM -0700, Chris Torek wrote: > On Tue, Apr 13, 2021 at 5:18 PM Sam Bostock <sam.bostock@shopify.com> wrote: > > Long story short, it seems to me that `git fetch` should update > > "refs/remotes/origin/HEAD" when the upstream HEAD changes, but it > > doesn't. > > It's never been the *intent* to have `git fetch` update > the corresponding remote-tracking `HEAD` ref. To make > that happen, you must run `git remote`: > > git remote set-head origin -a > > for instance. > > I have, however, often thought that this is the wrong > *default* way for things to work, and that at least by default, > `git fetch origin` should update `origin/HEAD` if the > fetch result indicates that it should. See also Junio's > reply. I think a configuration knob (similar to `fetch.prune`) > would be reasonable here. Users could then be encouraged > to set `fetch.prune` to `true`, and `fetch.update-remote-HEAD` > (or whatever) to `true` as well. I think so, too. The previous discussion Junio referred to it is here: https://lore.kernel.org/git/20201118091219.3341585-1-felipe.contreras@gmail.com/ If you do read it, note that the parts of the conversation about unborn heads are out of date. We do pick this up via clone these days, courtesy of the commits in 69571dfe21 (Merge branch 'jt/clone-unborn-head', 2021-02-17). -Peff ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-14 0:26 ` Chris Torek 2021-04-14 5:29 ` Jeff King @ 2021-04-14 10:56 ` Ævar Arnfjörð Bjarmason 2021-04-14 12:03 ` Andreas Schwab 2021-04-15 9:28 ` Jeff King 1 sibling, 2 replies; 10+ messages in thread From: Ævar Arnfjörð Bjarmason @ 2021-04-14 10:56 UTC (permalink / raw) To: Chris Torek; +Cc: Sam Bostock, Git List On Wed, Apr 14 2021, Chris Torek wrote: > On Tue, Apr 13, 2021 at 5:18 PM Sam Bostock <sam.bostock@shopify.com> wrote: >> Long story short, it seems to me that `git fetch` should update >> "refs/remotes/origin/HEAD" when the upstream HEAD changes, but it >> doesn't. > > It's never been the *intent* to have `git fetch` update > the corresponding remote-tracking `HEAD` ref. To make > that happen, you must run `git remote`: > > git remote set-head origin -a > > for instance. > > I have, however, often thought that this is the wrong > *default* way for things to work, and that at least by default, > `git fetch origin` should update `origin/HEAD` if the > fetch result indicates that it should. See also Junio's > reply. I think a configuration knob (similar to `fetch.prune`) > would be reasonable here. Users could then be encouraged > to set `fetch.prune` to `true`, and `fetch.update-remote-HEAD` > (or whatever) to `true` as well. As you'll see from the previous linked thread I happen to agree with you, but let's not step past that agreement and (no doubt subtly and unintentionally, in this case) misrepresent the other side, which also has a legitimate argument. Which is that this notion that "[a client should update its view of a remote to what a] fetch result indicates that it should" isn't something that exists, and that we ever had it is only an emergent implementation detail. So first of all, a "fetch result" doesn't look anything like that. Rather the server presents refs it has, and the client decides what it wants. Which is the start of the disconnect in mental models around this. What you see with "git ls-remote origin" != what you should expect to have at a local refs/remotes/origin/* after a fetch. Nothing in git itself actually needs this remote HEAD past clone time, and with 4f37d457065 (clone: respect remote unborn HEAD, 2021-02-05) there'll be even less reason to pay attention to it. We don't even always get it on "clone", we don't do it with "--bare", since the reason we do it is to one-time setup the default branch, which we then hardcode in the config in the non-bare case: [remote "origin"] url = https://github.com/git/git.git fetch = +refs/heads/*:refs/remotes/origin/* [branch "master"] remote = origin merge = refs/heads/master So arguably the bug is the other way around, that we should never save this information at all in the ref store at "clone" time, which would make "init && config && fetch" and "clone" consistent. I haven't looked, but wouldn't be surprised to discover that this was originally needed back when we needed to ferry information between shellscripts, and was just diligently retained when the relevant parts were rewritten in C. But I digress. Now, what people *do actually* legitimately use this information is a convenient local cache of "what's the main upstream branch?". I myself have written local scripts that used that, and been bitten by this information being stale / not there (in the case of init/config/fetch). But why does anyone need that? Well, I don't think they actually do. What they actually do want is to push or fetch the "main" branch. The "what was HEAD that one time I talked to this remote" is just a roundabout way of getting that. So isn't this whole thing just wart that we should fix in the protocol? Wouldn't the use-case for this be satisfied with something like: [branch "master"] remote = origin merge = HEAD ; does not work as you might expect Right now that will just push to refs/heads/HEAD, but what if we had a protocol extension to intercept it (or rather, some merge = <a name incompatible with a current push, maybe "$HEAD">, as an aside setting it to ":HEAD" has some very funny results) wouldn't that satisfy the use-case? After all, who's really interested in what the remote's idea of their HEAD when they last fetched is? Don't those users actually want the *current* idea of what HEAD is for the purposes of fetching or pushing? If we supported "I want the tip of your HEAD" (which we do) or "I have this ref update for you, on top of your idea of HEAD" (we don't) you could "git push" and it would do the right thing whether the primary branch was renamed from "master" to "main" during your "git push" or not. ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-14 10:56 ` Ævar Arnfjörð Bjarmason @ 2021-04-14 12:03 ` Andreas Schwab 2021-04-14 21:12 ` Junio C Hamano 2021-04-15 9:28 ` Jeff King 1 sibling, 1 reply; 10+ messages in thread From: Andreas Schwab @ 2021-04-14 12:03 UTC (permalink / raw) To: Ævar Arnfjörð Bjarmason; +Cc: Chris Torek, Sam Bostock, Git List On Apr 14 2021, Ævar Arnfjörð Bjarmason wrote: > Nothing in git itself actually needs this remote HEAD past clone time, > and with 4f37d457065 (clone: respect remote unborn HEAD, 2021-02-05) > there'll be even less reason to pay attention to it. Isn't that what git rev-parse origin resolves to? Andreas. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1 "And now for something completely different." ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-14 12:03 ` Andreas Schwab @ 2021-04-14 21:12 ` Junio C Hamano 0 siblings, 0 replies; 10+ messages in thread From: Junio C Hamano @ 2021-04-14 21:12 UTC (permalink / raw) To: Andreas Schwab Cc: Ævar Arnfjörð Bjarmason, Chris Torek, Sam Bostock, Git List Andreas Schwab <schwab@linux-m68k.org> writes: > On Apr 14 2021, Ævar Arnfjörð Bjarmason wrote: > >> Nothing in git itself actually needs this remote HEAD past clone time, >> and with 4f37d457065 (clone: respect remote unborn HEAD, 2021-02-05) >> there'll be even less reason to pay attention to it. > > Isn't that what git rev-parse origin resolves to? Correct. And that is why refs/remotes/origin/HEAD is defined to point at the branch that the owner of LOCAL repository considers is of interest, which may not be the same as what the owner of the REMOTE repository thinks is the primary branch in their worldview. ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: `git fetch` not updating 'origin/HEAD' after branch rename 2021-04-14 10:56 ` Ævar Arnfjörð Bjarmason 2021-04-14 12:03 ` Andreas Schwab @ 2021-04-15 9:28 ` Jeff King 1 sibling, 0 replies; 10+ messages in thread From: Jeff King @ 2021-04-15 9:28 UTC (permalink / raw) To: Ævar Arnfjörð Bjarmason; +Cc: Chris Torek, Sam Bostock, Git List On Wed, Apr 14, 2021 at 12:56:27PM +0200, Ævar Arnfjörð Bjarmason wrote: > Now, what people *do actually* legitimately use this information is a > convenient local cache of "what's the main upstream branch?". > > I myself have written local scripts that used that, and been bitten by > this information being stale / not there (in the case of > init/config/fetch). > > But why does anyone need that? Well, I don't think they actually > do. What they actually do want is to push or fetch the "main" > branch. The "what was HEAD that one time I talked to this remote" is > just a roundabout way of getting that. > > So isn't this whole thing just wart that we should fix in the protocol? > Wouldn't the use-case for this be satisfied with something like: > > [branch "master"] > remote = origin > merge = HEAD ; does not work as you might expect > > Right now that will just push to refs/heads/HEAD, but what if we had a > protocol extension to intercept it (or rather, some merge = <a name > incompatible with a current push, maybe "$HEAD">, as an aside setting it > to ":HEAD" has some very funny results) wouldn't that satisfy the > use-case? Keep in mind that if we do not have a cache, then finding out the remote HEAD involves a network trip. But we use branch.*.merge in lots of places that aren't fetch/push. E.g., how would "git rev-parse @{upstream}" work with the config you gave above? > After all, who's really interested in what the remote's idea of their > HEAD when they last fetched is? > > Don't those users actually want the *current* idea of what HEAD is for > the purposes of fetching or pushing? IMHO the cache of the remote HEAD in refs/remotes/origin/HEAD is the same as the cache of the remote refs in refs/remotes/origin/*. We only talk to the network during fetch/push operations, but it is convenient to have a local cache that names the things we saw there. As others mentioned, "git rev-parse origin" is another local command that works without touching the network. So I find the local cache of the remote HEAD quite useful. I think the only issue with it is that it is not kept up to date like the rest of the branches in refs/remotes/origin/*. That was an intentional decision, because you may want to define your own view of what is considered the default for the remote. But that is a much rarer case than people who do want to auto-update it on fetch (and for many years nobody cared too much, because people rarely updated HEAD anyway; but these days there's quite a lot of renaming going on). So it makes sense to at least provide a configurable option to allow updating it on each fetch. -Peff ^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2021-04-15 9:29 UTC | newest] Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-04-13 20:25 `git fetch` not updating 'origin/HEAD' after branch rename Sam Bostock 2021-04-13 20:37 ` Junio C Hamano 2021-04-13 21:09 ` Andreas Schwab 2021-04-13 21:22 ` Junio C Hamano 2021-04-14 0:26 ` Chris Torek 2021-04-14 5:29 ` Jeff King 2021-04-14 10:56 ` Ævar Arnfjörð Bjarmason 2021-04-14 12:03 ` Andreas Schwab 2021-04-14 21:12 ` Junio C Hamano 2021-04-15 9:28 ` Jeff King
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