* [PATCH] RFC: A new type of symbolic refs @ 2017-07-11 1:06 Stefan Beller 2017-07-16 13:04 ` Philip Oakley 2017-07-17 21:48 ` Junio C Hamano 0 siblings, 2 replies; 7+ messages in thread From: Stefan Beller @ 2017-07-11 1:06 UTC (permalink / raw) To: git; +Cc: Stefan Beller A symbolic ref can currently only point at (another symbolic) ref. However are use cases for symbolic refs to point at other things representing a commit-ish, such as gitlink entries in other repositories. In this use case we can use such a symbolic link to strengthen the relationship between a submodule and a superproject. Examples: 1) It makes it easier to explain when we recurse into submodules and to which sha1 the submodule is updated. Currently a submodule (or any repo) is either on a branch (i.e. HEAD is a symbolic ref) or is in 'detached HEAD' state (HEAD is a direct ref). For submodules it is wrong to be on its own branch if it wants to be controlled by the superproject as being on its own branch signals that the submodule is independent and can move the HEAD freely. Being in 'detached HEAD' state is the alternative to that and was chosen when git-submodule was implemented, but it is equally wrong; the lesser of two evils. Semantically the correct way to state a submodule is part of the superproject is by pointing its HEAD to the superproject. We do have "reset/checkout --recurse-submodules" now, but it is hard to explain what actually happens there (Which submodules are updated? All of them! -- But I want a subset only!) With this new mode of symbolic refs, any submodule that tracks the superproject, would 'automatically follow' the superproject as the submodules HEAD moves when the superproject changes. 2) "git -C submodule commit" would behave the same as it would on branch nowadays: It would make the commit in the submodule and then change the target of the symbolic ref which would be the index of the superproject! That implies that you do not need to 'git add' the submodule to the superproject, but have it done automatically. Signed-off-by: Stefan Beller <sbeller@google.com> --- cache.h | 2 ++ refs/files-backend.c | 10 ++++++++++ submodule.c | 40 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 52 insertions(+) diff --git a/cache.h b/cache.h index 71fe092644..4f79d23202 100644 --- a/cache.h +++ b/cache.h @@ -2029,4 +2029,6 @@ void sleep_millisec(int millisec); */ void safe_create_dir(const char *dir, int share); +extern int read_external_symref(struct strbuf *from, struct strbuf *out); + #endif /* CACHE_H */ diff --git a/refs/files-backend.c b/refs/files-backend.c index 0404f2c233..f56f7b87ce 100644 --- a/refs/files-backend.c +++ b/refs/files-backend.c @@ -713,6 +713,16 @@ static int files_read_raw_ref(struct ref_store *ref_store, goto out; } + if (starts_with(buf, "repo:")) { + if (read_external_symref(&sb_contents, referent)) { + *type |= REF_ISBROKEN; + ret = -1; + goto out; + } + *type |= REF_ISSYMREF; + ret = 0; + } + /* * Please note that FETCH_HEAD has additional * data after the sha. diff --git a/submodule.c b/submodule.c index da2b484879..7297f90485 100644 --- a/submodule.c +++ b/submodule.c @@ -2037,3 +2037,43 @@ int submodule_to_gitdir(struct strbuf *buf, const char *submodule) cleanup: return ret; } + +int read_external_symref(struct strbuf *from, struct strbuf *out) +{ + struct child_process cp = CHILD_PROCESS_INIT; + const char *repo, *gitlink; + int hint, code; + struct strbuf **split = strbuf_split(from, 0); + struct strbuf cmd_out = STRBUF_INIT; + + if (!split[0] || !split[1]) + return -1; + + repo = split[0]->buf + 5; /* skip 'repo:' */ + gitlink = split[1]->buf; + + argv_array_pushl(&cp.args, + "ignored-first-arg", + "-C", repo, + "ls-tree", "-z", "HEAD", "--", gitlink, NULL); + + /* + * 17 accounts for '160000 commit ', + * the \t before path and trailing \0. + */ + hint = 17 + GIT_SHA1_HEXSZ + split[1]->len; + code = capture_command(&cp, &cmd_out, hint); + + strbuf_release(split[0]); + strbuf_release(split[1]); + + if (!code) { + strbuf_reset(out); + strbuf_add(out, cmd_out.buf + strlen("160000 commit "), + GIT_SHA1_HEXSZ); + } else + return -1; + + return 0; +} + -- 2.13.2.695.g117ddefdb4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] RFC: A new type of symbolic refs 2017-07-11 1:06 [PATCH] RFC: A new type of symbolic refs Stefan Beller @ 2017-07-16 13:04 ` Philip Oakley 2017-07-16 14:20 ` Philip Oakley 2017-07-17 19:21 ` Stefan Beller 2017-07-17 21:48 ` Junio C Hamano 1 sibling, 2 replies; 7+ messages in thread From: Philip Oakley @ 2017-07-16 13:04 UTC (permalink / raw) To: Stefan Beller, git; +Cc: Stefan Beller From: "Stefan Beller" <sbeller@google.com> Sent: Tuesday, July 11, 2017 2:06 AM >A symbolic ref can currently only point at (another symbolic) ref. > However are use cases for symbolic refs to point at other things > representing a commit-ish, such as gitlink entries in other > repositories. In this use case we can use such a symbolic link > to strengthen the relationship between a submodule and a superproject. > Examples: If I understand this correctly, the new type is the 'starts_with(buf, ))'. It just wasn't obvious from the text that the new type is "repo:" as you never spell it out in the commit message. Should it be included in the message? Have I understood correctly? -- Philip [I'll be off-line till Friday, so will pick up then] > > 1) It makes it easier to explain when we recurse into submodules and > to which sha1 the submodule is updated. > > Currently a submodule (or any repo) is either on a branch (i.e. > HEAD is a symbolic ref) or is in 'detached HEAD' state (HEAD is > a direct ref). > For submodules it is wrong to be on its own branch if it wants to be > controlled by the superproject as being on its own branch signals that > the submodule is independent and can move the HEAD freely. > Being in 'detached HEAD' state is the alternative to that and was > chosen when git-submodule was implemented, but it is equally wrong; > the lesser of two evils. > > Semantically the correct way to state a submodule is part of the > superproject is by pointing its HEAD to the superproject. > > We do have "reset/checkout --recurse-submodules" now, but it is > hard to explain what actually happens there (Which submodules are > updated? All of them! -- But I want a subset only!) > > With this new mode of symbolic refs, any submodule that tracks the > superproject, would 'automatically follow' the superproject as the > submodules HEAD moves when the superproject changes. > > 2) "git -C submodule commit" would behave the same as it would on branch > nowadays: It would make the commit in the submodule and then change > the target of the symbolic ref which would be the index of the > superproject! That implies that you do not need to 'git add' the > submodule to the superproject, but have it done automatically. > > Signed-off-by: Stefan Beller <sbeller@google.com> > --- > cache.h | 2 ++ > refs/files-backend.c | 10 ++++++++++ > submodule.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 52 insertions(+) > > diff --git a/cache.h b/cache.h > index 71fe092644..4f79d23202 100644 > --- a/cache.h > +++ b/cache.h > @@ -2029,4 +2029,6 @@ void sleep_millisec(int millisec); > */ > void safe_create_dir(const char *dir, int share); > > +extern int read_external_symref(struct strbuf *from, struct strbuf *out); > + > #endif /* CACHE_H */ > diff --git a/refs/files-backend.c b/refs/files-backend.c > index 0404f2c233..f56f7b87ce 100644 > --- a/refs/files-backend.c > +++ b/refs/files-backend.c > @@ -713,6 +713,16 @@ static int files_read_raw_ref(struct ref_store > *ref_store, > goto out; > } > > + if (starts_with(buf, "repo:")) { > + if (read_external_symref(&sb_contents, referent)) { > + *type |= REF_ISBROKEN; > + ret = -1; > + goto out; > + } > + *type |= REF_ISSYMREF; > + ret = 0; > + } > + > /* > * Please note that FETCH_HEAD has additional > * data after the sha. > diff --git a/submodule.c b/submodule.c > index da2b484879..7297f90485 100644 > --- a/submodule.c > +++ b/submodule.c > @@ -2037,3 +2037,43 @@ int submodule_to_gitdir(struct strbuf *buf, const > char *submodule) > cleanup: > return ret; > } > + > +int read_external_symref(struct strbuf *from, struct strbuf *out) > +{ > + struct child_process cp = CHILD_PROCESS_INIT; > + const char *repo, *gitlink; > + int hint, code; > + struct strbuf **split = strbuf_split(from, 0); > + struct strbuf cmd_out = STRBUF_INIT; > + > + if (!split[0] || !split[1]) > + return -1; > + > + repo = split[0]->buf + 5; /* skip 'repo:' */ > + gitlink = split[1]->buf; > + > + argv_array_pushl(&cp.args, > + "ignored-first-arg", > + "-C", repo, > + "ls-tree", "-z", "HEAD", "--", gitlink, NULL); > + > + /* > + * 17 accounts for '160000 commit ', > + * the \t before path and trailing \0. > + */ > + hint = 17 + GIT_SHA1_HEXSZ + split[1]->len; > + code = capture_command(&cp, &cmd_out, hint); > + > + strbuf_release(split[0]); > + strbuf_release(split[1]); > + > + if (!code) { > + strbuf_reset(out); > + strbuf_add(out, cmd_out.buf + strlen("160000 commit "), > + GIT_SHA1_HEXSZ); > + } else > + return -1; > + > + return 0; > +} > + > -- > 2.13.2.695.g117ddefdb4 > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] RFC: A new type of symbolic refs 2017-07-16 13:04 ` Philip Oakley @ 2017-07-16 14:20 ` Philip Oakley 2017-07-17 19:21 ` Stefan Beller 1 sibling, 0 replies; 7+ messages in thread From: Philip Oakley @ 2017-07-16 14:20 UTC (permalink / raw) To: Stefan Beller, git; +Cc: Stefan Beller From: "Philip Oakley" <philipoakley@iee.org> > From: "Stefan Beller" <sbeller@google.com> > Sent: Tuesday, July 11, 2017 2:06 AM >>A symbolic ref can currently only point at (another symbolic) ref. >> However are use cases for symbolic refs to point at other things >> representing a commit-ish, such as gitlink entries in other >> repositories. In this use case we can use such a symbolic link >> to strengthen the relationship between a submodule and a superproject. >> Examples: > > If I understand this correctly, the new type is the 'starts_with(buf, ))'. Oops, my mistaken message prep accidently removed the "repo:" from the above. > > It just wasn't obvious from the text that the new type is "repo:" as you > never spell it out in the commit message. Should it be included in the > message? > > Have I understood correctly? > > -- > Philip > [I'll be off-line till Friday, so will pick up then] > >> >> 1) It makes it easier to explain when we recurse into submodules and >> to which sha1 the submodule is updated. >> >> Currently a submodule (or any repo) is either on a branch (i.e. >> HEAD is a symbolic ref) or is in 'detached HEAD' state (HEAD is >> a direct ref). >> For submodules it is wrong to be on its own branch if it wants to be >> controlled by the superproject as being on its own branch signals that >> the submodule is independent and can move the HEAD freely. >> Being in 'detached HEAD' state is the alternative to that and was >> chosen when git-submodule was implemented, but it is equally wrong; >> the lesser of two evils. >> >> Semantically the correct way to state a submodule is part of the >> superproject is by pointing its HEAD to the superproject. >> >> We do have "reset/checkout --recurse-submodules" now, but it is >> hard to explain what actually happens there (Which submodules are >> updated? All of them! -- But I want a subset only!) >> >> With this new mode of symbolic refs, any submodule that tracks the >> superproject, would 'automatically follow' the superproject as the >> submodules HEAD moves when the superproject changes. >> >> 2) "git -C submodule commit" would behave the same as it would on branch >> nowadays: It would make the commit in the submodule and then change >> the target of the symbolic ref which would be the index of the >> superproject! That implies that you do not need to 'git add' the >> submodule to the superproject, but have it done automatically. >> >> Signed-off-by: Stefan Beller <sbeller@google.com> >> --- >> cache.h | 2 ++ >> refs/files-backend.c | 10 ++++++++++ >> submodule.c | 40 ++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 52 insertions(+) >> >> diff --git a/cache.h b/cache.h >> index 71fe092644..4f79d23202 100644 >> --- a/cache.h >> +++ b/cache.h >> @@ -2029,4 +2029,6 @@ void sleep_millisec(int millisec); >> */ >> void safe_create_dir(const char *dir, int share); >> >> +extern int read_external_symref(struct strbuf *from, struct strbuf >> *out); >> + >> #endif /* CACHE_H */ >> diff --git a/refs/files-backend.c b/refs/files-backend.c >> index 0404f2c233..f56f7b87ce 100644 >> --- a/refs/files-backend.c >> +++ b/refs/files-backend.c >> @@ -713,6 +713,16 @@ static int files_read_raw_ref(struct ref_store >> *ref_store, >> goto out; >> } >> >> + if (starts_with(buf, "repo:")) { >> + if (read_external_symref(&sb_contents, referent)) { >> + *type |= REF_ISBROKEN; >> + ret = -1; >> + goto out; >> + } >> + *type |= REF_ISSYMREF; >> + ret = 0; >> + } >> + >> /* >> * Please note that FETCH_HEAD has additional >> * data after the sha. >> diff --git a/submodule.c b/submodule.c >> index da2b484879..7297f90485 100644 >> --- a/submodule.c >> +++ b/submodule.c >> @@ -2037,3 +2037,43 @@ int submodule_to_gitdir(struct strbuf *buf, const >> char *submodule) >> cleanup: >> return ret; >> } >> + >> +int read_external_symref(struct strbuf *from, struct strbuf *out) >> +{ >> + struct child_process cp = CHILD_PROCESS_INIT; >> + const char *repo, *gitlink; >> + int hint, code; >> + struct strbuf **split = strbuf_split(from, 0); >> + struct strbuf cmd_out = STRBUF_INIT; >> + >> + if (!split[0] || !split[1]) >> + return -1; >> + >> + repo = split[0]->buf + 5; /* skip 'repo:' */ >> + gitlink = split[1]->buf; >> + >> + argv_array_pushl(&cp.args, >> + "ignored-first-arg", >> + "-C", repo, >> + "ls-tree", "-z", "HEAD", "--", gitlink, NULL); >> + >> + /* >> + * 17 accounts for '160000 commit ', >> + * the \t before path and trailing \0. >> + */ >> + hint = 17 + GIT_SHA1_HEXSZ + split[1]->len; >> + code = capture_command(&cp, &cmd_out, hint); >> + >> + strbuf_release(split[0]); >> + strbuf_release(split[1]); >> + >> + if (!code) { >> + strbuf_reset(out); >> + strbuf_add(out, cmd_out.buf + strlen("160000 commit "), >> + GIT_SHA1_HEXSZ); >> + } else >> + return -1; >> + >> + return 0; >> +} >> + >> -- >> 2.13.2.695.g117ddefdb4 >> > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] RFC: A new type of symbolic refs 2017-07-16 13:04 ` Philip Oakley 2017-07-16 14:20 ` Philip Oakley @ 2017-07-17 19:21 ` Stefan Beller 1 sibling, 0 replies; 7+ messages in thread From: Stefan Beller @ 2017-07-17 19:21 UTC (permalink / raw) To: Philip Oakley; +Cc: git@vger.kernel.org On Sun, Jul 16, 2017 at 6:04 AM, Philip Oakley <philipoakley@iee.org> wrote: > > If I understand this correctly, the new type is the 'starts_with(buf, "repo:"))'. > > It just wasn't obvious from the text that the new type is "repo:" as you > never spell it out in the commit message. Should it be included in the > message? > > Have I understood correctly? Yes, you understood correctly. The idea is to allow submodules to "borrow" its refs from the superproject. My original idea was to only borrow HEAD from the superproject, but this can be extended to more branches. By having a more generic way of borrowing refs from another repo, this can also be a different repo than the superproject (I don't know the use case for this yet, but let's not have a to specific proposal). Let's see how this RFC fares in further interest from the community. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] RFC: A new type of symbolic refs 2017-07-11 1:06 [PATCH] RFC: A new type of symbolic refs Stefan Beller 2017-07-16 13:04 ` Philip Oakley @ 2017-07-17 21:48 ` Junio C Hamano 2017-07-17 23:22 ` Stefan Beller 1 sibling, 1 reply; 7+ messages in thread From: Junio C Hamano @ 2017-07-17 21:48 UTC (permalink / raw) To: Stefan Beller; +Cc: git Stefan Beller <sbeller@google.com> writes: > +int read_external_symref(struct strbuf *from, struct strbuf *out) > +{ > + struct child_process cp = CHILD_PROCESS_INIT; > + const char *repo, *gitlink; > + int hint, code; > + struct strbuf **split = strbuf_split(from, 0); > + struct strbuf cmd_out = STRBUF_INIT; > + > + if (!split[0] || !split[1]) > + return -1; > + > + repo = split[0]->buf + 5; /* skip 'repo:' */ > + gitlink = split[1]->buf; > + > + argv_array_pushl(&cp.args, > + "ignored-first-arg", > + "-C", repo, > + "ls-tree", "-z", "HEAD", "--", gitlink, NULL); > + > + /* > + * 17 accounts for '160000 commit ', > + * the \t before path and trailing \0. > + */ > + hint = 17 + GIT_SHA1_HEXSZ + split[1]->len; > + code = capture_command(&cp, &cmd_out, hint); > + > + strbuf_release(split[0]); > + strbuf_release(split[1]); > + > + if (!code) { > + strbuf_reset(out); > + strbuf_add(out, cmd_out.buf + strlen("160000 commit "), > + GIT_SHA1_HEXSZ); > + } else > + return -1; > + > + return 0; > +} This may help the initial checkout, but to be useful after that, we need to define what happens when an equivalent of "git update-ref HEAD" is done in the submodule repository, when HEAD is pointing elsewhere. The above only shows read-only operation, which is not all that interesting. I _think_ a symbolic HEAD that points upwards to the gitlink entry in the superproject's index is the easiest to understand and it is something we can define a clear and useful semantics for. When a recursive checkout of a branch 'foo' is made in the superproject, the index in the superproject would name the commit in the submodule to be checked out. We traditionally detech the HEAD at the submodule to that commit, but instead we could say "check the index of the superproject to see where the HEAD should be pointing at" in the submodule. Either way, immediately after such a recursive checkout, "git status" inside the submodule would find that the HEAD points at the commit recorded in the 'foo' branch of the superproject and things are clean. After you work in the submodule and make a commit, an equivalent of "git update-ref HEAD" is done behind the scene to update HEAD in the submodule. In the traditional world, that is done to detached HEAD and nothing else changes, but if the symref HEAD points upwards into the index of the superproject, what needs to be done is very obvious; we do "git add submodule" in the superproject. And this is not just limited to creating a commit in the submodule. "reset --hard HEAD~2" in the submodule to rewind the HEAD by two commits would also be an update to HEAD and through the symref-ness of the HEAD should result in an update to the index of the superproject. However, I do not think a good explanation of what should mean when this new-style symbolic HEAD points at a commit in the superproject, whether its limited to its HEAD or a tip of an arbitrary branch that may not even be checked out. These are not something we can easily change without affecting wider context. Our submodule, when we make a new commit, may be ready to advance, but our superproject and other submodules may not be ready to be included in a new commit in the superproject. So I think the idea this patch illustrates is on to something interesting and potentially useful, but I am not sure if it makes sense to tie it to anything but the index of the superproject. Even if we limit ourselves to pointing at the index of the superproject, there probably are a handful of interesting issues that need to be clarified (not in the sense of "this and that issues exist, so this won't be a useful feature", but in the sense of "we'd be able to do these useful things using this feature, and we need to fill in more details"), such as: - Making new commits in the submodule available to the upstream. Just like a detached HEAD in the submodule, this is not tied to any concrete branch, and it is unclear how a recursive "push" from the superproject should propagate the changes to the upstream of the submodule; - Switching between branches that bind the same commit for the submodule in the superproject would work just like switching between branches that record the same blob for a path, i.e. it will carry forward a local modification. - The index entry in the superproject may now have to get involved in fsck and reachability study in the submodule as reachability root. A corollary to this is that submodules behave more similarly to regular blobs wrt "git reset --hard" in the superproject, which is a good thing. "git -C submodule commit && git reset --hard" will create a new commit in the submodule, add it to the index of the superproject, and then lose that change from the index of the superproject, making the commit unreachable, just like "edit file && git add file && git reset --hard" in the superproject will make the blob that records the updated content of the file unreachable. Thanks. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] RFC: A new type of symbolic refs 2017-07-17 21:48 ` Junio C Hamano @ 2017-07-17 23:22 ` Stefan Beller 2017-07-18 19:03 ` Junio C Hamano 0 siblings, 1 reply; 7+ messages in thread From: Stefan Beller @ 2017-07-17 23:22 UTC (permalink / raw) To: Junio C Hamano; +Cc: git@vger.kernel.org On Mon, Jul 17, 2017 at 2:48 PM, Junio C Hamano <gitster@pobox.com> wrote: > I _think_ a symbolic HEAD that points upwards to the gitlink entry in > the superproject's index is the easiest to understand and it is > something we can define a clear and useful semantics for. ok, let's start with that. Once we have that we can see if that also makes sense for the non-submodule/superproject world. > When a recursive checkout of a branch 'foo' is made in the > superproject, the index in the superproject would name the commit in > the submodule to be checked out. We traditionally detech the HEAD > at the submodule to that commit, but instead we could say "check the > index of the superproject to see where the HEAD should be pointing > at" in the submodule. Either way, immediately after such a > recursive checkout, "git status" inside the submodule would find > that the HEAD points at the commit recorded in the 'foo' branch of > the superproject and things are clean. Right. > After you work in the submodule and make a commit, an equivalent of > "git update-ref HEAD" is done behind the scene to update HEAD in the > submodule. In the traditional world, that is done to detached HEAD > and nothing else changes, but if the symref HEAD points upwards into > the index of the superproject, what needs to be done is very obvious; > we do "git add submodule" in the superproject. And this is not just > limited to creating a commit in the submodule. "reset --hard HEAD~2" > in the submodule to rewind the HEAD by two commits would also be an > update to HEAD and through the symref-ness of the HEAD should result > in an update to the index of the superproject. agreed. we'd find out what HEAD~2 is and then write the gitlink in the superproject index to be that commit. > However, I do not think a good explanation of what should mean when > this new-style symbolic HEAD points at a commit in the superproject, > whether its limited to its HEAD or a tip of an arbitrary branch that > may not even be checked out. The proposal only inspects the currently staged value of a gitlink, there is no way to reference a specific commit or (non-checked-out) branch, so it is not possible to point at them with the given read syntax. So in case the superproject changes its HEAD (such as checking out a different branch, or detaching the HEAD), then the submodules HEAD changes automatically as the superprojects tree may change. > These are not something we can easily > change without affecting wider context. Our submodule, when we make > a new commit, may be ready to advance, but our superproject and > other submodules may not be ready to be included in a new commit in > the superproject. That is an interesting problem, as un-staging the submodule is not as easy as un-staging a change in a file. Assume we have a layout as git init super git -C super init sub echo change >>super/sub/file git -C super/sub commit -a -m "submodule changes" then the following behaviors seem reasonable: git -C super reset --soft sub As the superprojects index is not touched, so is the submodules HEAD and working tree. The submodule stays as is. git -C super reset --mixed sub As this resets the index of the superproject, but not the working tree, I'd expect the submodules HEAD to be detached keeping the new content alive, such that it can be added as git -C super add --re-attach-with-new-symref-mode sub git -C super reset --hard sub This resets the index and the working tree in the superproject, so the submodules commit with the new content would be lost, the submodules HEAD is still the new symbolic ref. The subs working tree is dirty and contains the change unless --recurse-submodules is given in addition, which would wipe the subs working directory in addition. > So I think the idea this patch illustrates is on to something > interesting and potentially useful, but I am not sure if it makes > sense to tie it to anything but the index of the superproject. Hypothetical use case: Your project targets multiple platforms and you are interested in not producing the perfect history like we do, but you never change a commit once created (for policy legal reasons). Naturally this produces a lot of duds. Create a a gitlink for each platform that points to the latest commit known to work for the platform. Point HEAD to the repository *itself*, and gitlink of the platform that you want to follow. After each fetch, checking out the latest HEAD is known to work for your platform. (This hypothetical HEAD reference to itself is entertaining for sure.) > Even if we limit ourselves to pointing at the index of the > superproject, there probably are a handful of interesting issues > that need to be clarified (not in the sense of "this and that issues > exist, so this won't be a useful feature", but in the sense of "we'd > be able to do these useful things using this feature, and we need to > fill in more details"), such as: > > - Making new commits in the submodule available to the upstream. > Just like a detached HEAD in the submodule, this is not tied to > any concrete branch, and it is unclear how a recursive "push" > from the superproject should propagate the changes to the > upstream of the submodule; In Gerrit land people are trained to use git push HEAD:refs/for/master which would work fine when propagated to the submodule as-is. There are two answers for the life without Gerrit in a dumb git remote. (a) In the far future in the ideal world, where version control is a solved problem, submodules can reside inside the superproject on the remote as well, i.e. in $GIT_DIR/modules/name, the URL may be twisted to not expose the "modules/name" part, though such that example.org/superproject example.org/superproject/submodule is possible. In this world a push of the superproject would also transfer the relevant submodule commits, such that the remote has all of the submodules history that contains all gitlink entries. Pushing from inside the submodule may either push the superproject (as you can push from a directory of the superproject) or it would abort to not confuse a user. (b) In the near future, I have no idea how to best solve this. Maybe we can push it as a detached HEAD to the remote? > - Switching between branches that bind the same commit for the > submodule in the superproject would work just like switching > between branches that record the same blob for a path, i.e. it > will carry forward a local modification. Right. > > - The index entry in the superproject may now have to get involved > in fsck and reachability study in the submodule as reachability > root. A corollary to this is that submodules behave more > similarly to regular blobs wrt "git reset --hard" in the > superproject, which is a good thing. "git -C submodule commit && > git reset --hard" will create a new commit in the submodule, add > it to the index of the superproject, and then lose that change > from the index of the superproject, making the commit > unreachable, just like "edit file && git add file && git reset > --hard" in the superproject will make the blob that records the > updated content of the file unreachable. This is in sync with my understanding above. Thanks, Stefan ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] RFC: A new type of symbolic refs 2017-07-17 23:22 ` Stefan Beller @ 2017-07-18 19:03 ` Junio C Hamano 0 siblings, 0 replies; 7+ messages in thread From: Junio C Hamano @ 2017-07-18 19:03 UTC (permalink / raw) To: Stefan Beller; +Cc: git@vger.kernel.org Stefan Beller <sbeller@google.com> writes: >> Even if we limit ourselves to pointing at the index of the >> superproject, there probably are a handful of interesting issues >> that need to be clarified (not in the sense of "this and that issues >> exist, so this won't be a useful feature", but in the sense of "we'd >> be able to do these useful things using this feature, and we need to >> fill in more details"), such as: >> >> - Making new commits in the submodule available to the upstream. >> Just like a detached HEAD in the submodule, this is not tied to >> any concrete branch, and it is unclear how a recursive "push" >> from the superproject should propagate the changes to the >> upstream of the submodule; > > In Gerrit land people are trained to use > git push HEAD:refs/for/master > which would work fine when propagated to the submodule as-is. What I was alluding to is how you find 'master' in 'for/master', given the submodule HEAD which only says "I point at the index of the superproject". Note that 'master' here refers to a branch in the submodule. If we further limit ourselves and declare that a submodule that uses this external-reference as HEAD must always be on the same branch as the superproject is on, then we can find what branch the superproject is on, and use that. ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2017-07-18 19:04 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2017-07-11 1:06 [PATCH] RFC: A new type of symbolic refs Stefan Beller 2017-07-16 13:04 ` Philip Oakley 2017-07-16 14:20 ` Philip Oakley 2017-07-17 19:21 ` Stefan Beller 2017-07-17 21:48 ` Junio C Hamano 2017-07-17 23:22 ` Stefan Beller 2017-07-18 19:03 ` Junio C Hamano
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