git/ls-refs.c, branch v2.32.2

Merge branch 'jt/clone-unborn-head'

2021-02-18T01:21:40Z

"git clone" tries to locally check out the branch pointed at by HEAD of the remote repository after it is done, but the protocol did not convey the information necessary to do so when copying an empty repository. The protocol v2 learned how to do so. * jt/clone-unborn-head: clone: respect remote unborn HEAD connect, transport: encapsulate arg in struct ls-refs: report unborn targets of symrefs

Merge branch 'tb/ls-refs-optim'

2021-02-06T00:40:45Z

The ls-refs protocol operation has been optimized to narrow the sub-hierarchy of refs/ it walks to produce response. * tb/ls-refs-optim: ls-refs.c: traverse prefixes of disjoint "ref-prefix" sets ls-refs.c: initialize 'prefixes' before using it refs: expose 'for_each_fullref_in_prefixes'

ls-refs: report unborn targets of symrefs

2021-02-05T21:49:53Z

When cloning, we choose the default branch based on the remote HEAD. But if there is no remote HEAD reported (which could happen if the target of the remote HEAD is unborn), we'll fall back to using our local init.defaultBranch. Traditionally this hasn't been a big deal, because most repos used "master" as the default. But these days it is likely to cause confusion if the server and client implementations choose different values (e.g., if the remote started with "main", we may choose "master" locally, create commits there, and then the user is surprised when they push to "master" and not "main"). To solve this, the remote needs to communicate the target of the HEAD symref, even if it is unborn, and "git clone" needs to use this information. Currently, symrefs that have unborn targets (such as in this case) are not communicated by the protocol. Teach Git to advertise and support the "unborn" feature in "ls-refs" (by default, this is advertised, but server administrators may turn this off through the lsrefs.unborn config). This feature indicates that "ls-refs" supports the "unborn" argument; when it is specified, "ls-refs" will send the HEAD symref with the name of its unborn target. This change is only for protocol v2. A similar change for protocol v0 would require independent protocol design (there being no analogous position to signal support for "unborn") and client-side plumbing of the data required, so the scope of this patch set is limited to protocol v2. The client side will be updated to use this in a subsequent commit. Signed-off-by: Jonathan Tan Signed-off-by: Junio C Hamano

ls-refs.c: traverse prefixes of disjoint "ref-prefix" sets

2021-01-23T02:57:27Z

ls-refs performs a single revision walk over the whole ref namespace, and sends ones that match with one of the given ref prefixes down to the user. This can be expensive if there are many refs overall, but the portion of them covered by the given prefixes is small by comparison. To attempt to reduce the difference between the number of refs traversed, and the number of refs sent, only traverse references which are in the longest common prefix of the given prefixes. This is very reminiscent of the approach taken in b31e2680c4 (ref-filter.c: find disjoint pattern prefixes, 2019-06-26) which does an analogous thing for multi-patterned 'git for-each-ref' invocations. The callback 'send_ref' is resilient to ignore extra patterns by discarding any arguments which do not begin with at least one of the specified prefixes. Similarly, the code introduced in b31e2680c4 is resilient to stop early at metacharacters, but we only pass strict prefixes here. At worst we would return too many results, but the double checking done by send_ref will throw away anything that doesn't start with something in the prefix list. Finally, if no prefixes were provided, then implicitly add the empty string (which will match all references) since this matches the existing behavior (see the "no restrictions" comment in "ls-refs.c:ref_match()"). Original-patch-by: Jacob Vosmaer Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano

ls-refs.c: initialize 'prefixes' before using it

2021-01-23T02:57:27Z

Correctly initialize the "prefixes" strvec using strvec_init() instead of simply zeroing it via the earlier memset(). There's no way to trigger a crash, since the first 'ref-prefix' command will initialize the strvec via the 'ALLOC_GROW' in 'strvec_push_nodup()' (the alloc and nr variables are already zero'd, so the call to ALLOC_GROW is valid). If no "ref-prefix" command was given, then the call to 'ls-refs.c:ref_match()' will abort early after it reads the zero in 'prefixes->nr'. Likewise, strvec_clear() will only call free() on the array, which is NULL, so we're safe there, too. But, all of this is dangerous and requires more reasoning than it would if we simply called 'strvec_init()', so do that. Signed-off-by: Jacob Vosmaer Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano

refs: switch peel_ref() to peel_iterated_oid()

2021-01-21T23:51:31Z

The peel_ref() interface is confusing and error-prone: - it's typically used by ref iteration callbacks that have both a refname and oid. But since they pass only the refname, we may load the ref value from the filesystem again. This is inefficient, but also means we are open to a race if somebody simultaneously updates the ref. E.g., this: int some_ref_cb(const char *refname, const struct object_id *oid, ...) { if (!peel_ref(refname, &peeled)) printf("%s peels to %s", oid_to_hex(oid), oid_to_hex(&peeled); } could print nonsense. It is correct to say "refname peels to..." (you may see the "before" value or the "after" value, either of which is consistent), but mentioning both oids may be mixing before/after values. Worse, whether this is possible depends on whether the optimization to read from the current iterator value kicks in. So it is actually not possible with: for_each_ref(some_ref_cb); but it _is_ possible with: head_ref(some_ref_cb); which does not use the iterator mechanism (though in practice, HEAD should never peel to anything, so this may not be triggerable). - it must take a fully-qualified refname for the read_ref_full() code path to work. Yet we routinely pass it partial refnames from callbacks to for_each_tag_ref(), etc. This happens to work when iterating because there we do not call read_ref_full() at all, and only use the passed refname to check if it is the same as the iterator. But the requirements for the function parameters are quite unclear. Instead of taking a refname, let's instead take an oid. That fixes both problems. It's a little funny for a "ref" function not to involve refs at all. The key thing is that it's optimizing under the hood based on having access to the ref iterator. So let's change the name to make it clear why you'd want this function versus just peel_object(). There are two other directions I considered but rejected: - we could pass the peel information into the each_ref_fn callback. However, we don't know if the caller actually wants it or not. For packed-refs, providing it is essentially free. But for loose refs, we actually have to peel the object, which would be wasteful in most cases. We could likewise pass in a flag to the callback indicating whether the peeled information is known, but that complicates those callbacks, as they then have to decide whether to manually peel themselves. Plus it requires changing the interface of every callback, whether they care about peeling or not, and there are many of them. - we could make a function to return the peeled value of the current iterated ref (computing it if necessary), and BUG() otherwise. I.e.: int peel_current_iterated_ref(struct object_id *out); Each of the current callers is an each_ref_fn callback, so they'd mostly be happy. But: - we use those callbacks with functions like head_ref(), which do not use the iteration code. So we'd need to handle the fallback case there, anyway. - it's possible that a caller would want to call into generic code that sometimes is used during iteration and sometimes not. This encapsulates the logic to do the fast thing when possible, and fallback when necessary. The implementation is mostly obvious, but I want to call out a few things in the patch: - the test-tool coverage for peel_ref() is now meaningless, as it all collapses to a single peel_object() call (arguably they were pretty uninteresting before; the tricky part of that function is the fast-path we see during iteration, but these calls didn't trigger that). I've just dropped it entirely, though note that some other tests relied on the tags we created; I've moved that creation to the tests where it matters. - we no longer need to take a ref_store parameter, since we'd never look up a ref now. We do still rely on a global "current iterator" variable which _could_ be kept per-ref-store. But in practice this is only useful if there are multiple recursive iterations, at which point the more appropriate solution is probably a stack of iterators. No caller used the actual ref-store parameter anyway (they all call the wrapper that passes the_repository). - the original only kicked in the optimization when the "refname" pointer matched (i.e., not string comparison). We do likewise with the "oid" parameter here, but fall back to doing an actual oideq() call. This in theory lets us kick in the optimization more often, though in practice no current caller cares. It should never be wrong, though (peeling is a property of an object, so two refs pointing to the same object would peel identically). - the original took care not to touch the peeled out-parameter unless we found something to put in it. But no caller cares about this, and anyway, it is enforced by peel_object() itself (and even in the optimized iterator case, that's where we eventually end up). We can shorten the code and avoid an extra copy by just passing the out-parameter through the stack. Signed-off-by: Jeff King Reviewed-by: Taylor Blau Signed-off-by: Junio C Hamano

strvec: rename struct fields

2020-07-31T02:18:06Z

The "argc" and "argv" names made sense when the struct was argv_array, but now they're just confusing. Let's rename them to "nr" (which we use for counts elsewhere) and "v" (which is rather terse, but reads well when combined with typical variable names like "args.v"). Note that we have to update all of the callers immediately. Playing tricks with the preprocessor is hard here, because we wouldn't want to rewrite unrelated tokens. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

strvec: convert more callers away from argv_array name

2020-07-28T22:02:18Z

We eventually want to drop the argv_array name and just use strvec consistently. There's no particular reason we have to do it all at once, or care about interactions between converted and unconverted bits. Because of our preprocessor compat layer, the names are interchangeable to the compiler (so even a definition and declaration using different names is OK). This patch converts remaining files from the first half of the alphabet, to keep the diff to a manageable size. The conversion was done purely mechanically with: git ls-files '*.c' '*.h' | xargs perl -i -pe ' s/ARGV_ARRAY/STRVEC/g; s/argv_array/strvec/g; ' and then selectively staging files with "git add '[abcdefghjkl]*'". We'll deal with any indentation/style fallouts separately. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

strvec: rename files from argv-array to strvec

2020-07-28T22:02:17Z

This requires updating #include lines across the code-base, but that's all fairly mechanical, and was done with: git ls-files '*.c' '*.h' | xargs perl -i -pe 's/argv-array.h/strvec.h/' Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

upload-pack: handle unexpected delim packets

2020-03-27T19:18:48Z

When processing the arguments list for a v2 ls-refs or fetch command, we loop like this: while (packet_reader_read(request) != PACKET_READ_FLUSH) { const char *arg = request->line; ...handle arg... } to read and handle packets until we see a flush. The hidden assumption here is that anything except PACKET_READ_FLUSH will give us valid packet data to read. But that's not true; PACKET_READ_DELIM or PACKET_READ_EOF will leave packet->line as NULL, and we'll segfault trying to look at it. Instead, we should follow the more careful model demonstrated on the client side (e.g., in process_capabilities_v2): keep looping as long as we get normal packets, and then make sure that we broke out of the loop due to a real flush. That fixes the segfault and correctly diagnoses any unexpected input from the client. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano