| Message ID | 20190626084139.30246-1-pclouds@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [PATCH/RFC] get_oid: new extended SHA-1 syntax to control resolution process | expand |
Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes: > The problem is we try every possible way to resolve a rev. Let's have > some annotation to express that we only want to resolve a rev in a > certain way: > > - <hash>@{hash} only accepts a full hash or a short hash. If it's a > short hash, it cannot be ambiguous. This is to defeat something like refs/heads/deadbeef (the branch whose name is "deadbeef") interfering an object whose name begins with that hexadecimal substring. Makes sense. > - <ref>@{literal} only accepts full ref. No turning "master" into > "refs/heads/master". This is already doable by saying "refs/heads/master", isn't it? Any ambiguous ones like a branch or a tag whose name is 'refs/heads/master' (i.e. refs/heads/refs/heads/master and refs/tags/refs/heads/master respectively) won't interfere once you use the explicit prefix refs/ like so. I'd rather not to see this one added. > - <output>@{describe} interprets <output> as git-describe output > only, not an object name or a reference. Again this is to defeat refs/heads/v2.22.0-221-gdeadbeef branch interferring with the object "deadbeef" thusly described. Makes sense. In the above, my two "Makes sense" only refer to the capability the syntax allows us to have, not the suggested syntax itself (which I am not convinced is a good use of @{<token>} yet). Thanks.
On Thu, Jun 27, 2019 at 1:51 AM Junio C Hamano <gitster@pobox.com> wrote: > > - <ref>@{literal} only accepts full ref. No turning "master" into > > "refs/heads/master". > > This is already doable by saying "refs/heads/master", isn't it? Any > ambiguous ones like a branch or a tag whose name is 'refs/heads/master' > (i.e. refs/heads/refs/heads/master and refs/tags/refs/heads/master > respectively) won't interfere once you use the explicit prefix refs/ > like so. I'd rather not to see this one added. If refs/heads/master does _not_ exist, then ref/heads/master can resolve to refs/heads/refs/heads/master, which I think is unexpected. "ref not found" error or something should be returned instead.
Duy Nguyen <pclouds@gmail.com> writes: > If refs/heads/master does _not_ exist, then ref/heads/master can > resolve to refs/heads/refs/heads/master, which I think is unexpected. > "ref not found" error or something should be returned instead. Ah, that was what I missed. Thanks.
Bikeshed painting ahead. Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes: [...] > The problem is we try every possible way to resolve a rev. Let's have > some annotation to express that we only want to resolve a rev in a > certain way: > > - <hash>@{hash} only accepts a full hash or a short hash. If it's a > short hash, it cannot be ambiguous. > > - <ref>@{literal} only accepts full ref. No turning "master" into > "refs/heads/master". > > - <output>@{describe} interprets <output> as git-describe output > only, not an object name or a reference. > > This gives scripts much better control over get_oid(), which > translates to rev-parse and a bunch other commands. > > PS. The new syntax can stack with existing ones. E.g. you could write > refs/heads/master@{literal}@{yesterday} or <hash>@{hash}^{tree}. > Perhaps I should allow these tags at the end too, so you can enforce a > variable like "$REV"@{literal} where $REV could be even HEAD~123 I think it would be better to use <hash>^{hash} instead of <hash>@{hash}. The <ref-ish>@{<something>} is used currently for information that is outside the DAG, like @{<date>}, @{<n>}, @{-<n>} uses information from reflog, and @{upstream} and @{push} uses information from the config. On the other hand ^{<type>}, ^{/<search text>}, and the future ^{<hashalgo>} all use DAG-only information. Though one could argue that refs information _is_ outside the DAG... P.S. We have 'git show-ref --verify' that requires exact match (no DWIM-mery), which can be used together with '--quiet' in a script. But this doesn't allow for checking if an exact match, or a describe output exists in repository. Thanks for taking it up, -- Jakub Narębski
On Sun, Jun 30, 2019 at 4:30 PM Jakub Narebski <jnareb@gmail.com> wrote: > > Bikeshed painting ahead. > > Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes: > [...] > > The problem is we try every possible way to resolve a rev. Let's have > > some annotation to express that we only want to resolve a rev in a > > certain way: > > > > - <hash>@{hash} only accepts a full hash or a short hash. If it's a > > short hash, it cannot be ambiguous. > > > > - <ref>@{literal} only accepts full ref. No turning "master" into > > "refs/heads/master". > > > > - <output>@{describe} interprets <output> as git-describe output > > only, not an object name or a reference. > > > > This gives scripts much better control over get_oid(), which > > translates to rev-parse and a bunch other commands. > > > > PS. The new syntax can stack with existing ones. E.g. you could write > > refs/heads/master@{literal}@{yesterday} or <hash>@{hash}^{tree}. > > Perhaps I should allow these tags at the end too, so you can enforce a > > variable like "$REV"@{literal} where $REV could be even HEAD~123 > > I think it would be better to use <hash>^{hash} instead of > <hash>@{hash}. > > The <ref-ish>@{<something>} is used currently for information that is > outside the DAG, like @{<date>}, @{<n>}, @{-<n>} uses information from > reflog, and @{upstream} and @{push} uses information from the config. > > On the other hand ^{<type>}, ^{/<search text>}, and the future > ^{<hashalgo>} all use DAG-only information. I wasn't aware of ^{<hashalgo>}. hash-function-transition.txt is a bit light on the exact behavior, but maybe we can just define it like <hash>@{hash} in this thread (then we don't even need to introduce @{hash})? That is, if <hash>^{<hashalgo>} fails to find a matching object, the get_oid() result is "not found", there will be no further attempt to interpret the given revision in a different way (e.g. try to see if the same ref exists...). It also means <hash>^{<hashalgo>} will remain supported even after the sha-512 transition period. @{describe} might go the same way as @{hash} (that is, becoming ^{describe}). I think it's just a slightly different way to write hashes. > Though one could argue that refs information _is_ outside the DAG... Refs info is outside DAG. But that's mostly for <ref>@{literal} and it allows something like <ref>@{literal}@{upstream}. But hash (or object name) is already used inside DAG (to link between commits, trees and blobs). Though one might still argue that's only true for full hash, not short ones.
diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt index 82c1e5754e..93eb278743 100644 --- a/Documentation/revisions.txt +++ b/Documentation/revisions.txt @@ -86,6 +86,16 @@ some output processing may assume ref names in UTF-8. immediately following a ref name and the ref must have an existing log ('$GIT_DIR/logs/<refname>'). +'<refname>@{literal}':: + The ref is not expanded by Git. In other words, if '$GIT_DIR/<refname>' + does not exist, the ref is not valid. + +'<sha1>@{hash}':: + '<sha1>' must be an unambiguous (short or full) object name. + +'<describeOutput>@{describe}':: + ... + '@{<n>}', e.g. '@\{1\}':: You can use the '@' construct with an empty ref part to get at a reflog entry of the current branch. For example, if you are on diff --git a/refs.c b/refs.c index b8a8430c96..2ee33257fd 100644 --- a/refs.c +++ b/refs.c @@ -634,6 +634,27 @@ int repo_dwim_ref(struct repository *r, const char *str, int len, return refs_found; } +int repo_dwim_ref_strict(struct repository *r, + const char *str, int len, + struct object_id *oid, + char **ref) +{ + char *last_branch = substitute_branch_name(r, &str, &len); + struct strbuf sb = STRBUF_INIT; + int flag; + + FREE_AND_NULL(last_branch); + strbuf_add(&sb, str, len); + *ref = xstrdup_or_null( + refs_resolve_ref_unsafe(get_main_ref_store(r), + sb.buf, + RESOLVE_REF_READING, + oid, + &flag)); + strbuf_release(&sb); + return *ref != NULL; +} + int dwim_ref(const char *str, int len, struct object_id *oid, char **ref) { return repo_dwim_ref(the_repository, str, len, oid, ref); @@ -673,8 +694,9 @@ int expand_ref(struct repository *repo, const char *str, int len, return refs_found; } -int repo_dwim_log(struct repository *r, const char *str, int len, - struct object_id *oid, char **log) +static int do_dwim_log(struct repository *r, const char *str, int len, + struct object_id *oid, char **log, + int ignore_rev_parse_rules) { struct ref_store *refs = get_main_ref_store(r); char *last_branch = substitute_branch_name(r, &str, &len); @@ -687,6 +709,9 @@ int repo_dwim_log(struct repository *r, const char *str, int len, struct object_id hash; const char *ref, *it; + if (ignore_rev_parse_rules && p != ref_rev_parse_rules) + break; + strbuf_reset(&path); strbuf_addf(&path, *p, len, str); ref = refs_resolve_ref_unsafe(refs, path.buf, @@ -713,6 +738,18 @@ int repo_dwim_log(struct repository *r, const char *str, int len, return logs_found; } +int repo_dwim_log(struct repository *r, const char *str, int len, + struct object_id *oid, char **log) +{ + return do_dwim_log(r, str, len, oid, log, 0); +} + +int repo_dwim_log_strict(struct repository *r, const char *str, int len, + struct object_id *oid, char **log) +{ + return do_dwim_log(r, str, len, oid, log, 1); +} + int dwim_log(const char *str, int len, struct object_id *oid, char **log) { return repo_dwim_log(the_repository, str, len, oid, log); diff --git a/refs.h b/refs.h index 730d05ad91..9395a2e708 100644 --- a/refs.h +++ b/refs.h @@ -151,6 +151,8 @@ void expand_ref_prefix(struct argv_array *prefixes, const char *prefix); int expand_ref(struct repository *r, const char *str, int len, struct object_id *oid, char **ref); int repo_dwim_ref(struct repository *r, const char *str, int len, struct object_id *oid, char **ref); int repo_dwim_log(struct repository *r, const char *str, int len, struct object_id *oid, char **ref); +int repo_dwim_ref_strict(struct repository *r, const char *str, int len, struct object_id *oid, char **ref); +int repo_dwim_log_strict(struct repository *r, const char *str, int len, struct object_id *oid, char **ref); int dwim_ref(const char *str, int len, struct object_id *oid, char **ref); int dwim_log(const char *str, int len, struct object_id *oid, char **ref); diff --git a/sha1-name.c b/sha1-name.c index 728e6f1f61..2d05414140 100644 --- a/sha1-name.c +++ b/sha1-name.c @@ -789,6 +789,25 @@ static inline int push_mark(const char *string, int len) return at_mark(string, len, suffix, ARRAY_SIZE(suffix)); } +static inline int literal_mark(const char *string, int len) +{ + const char *suffix[] = { "@{literal}" }; + return at_mark(string, len, suffix, ARRAY_SIZE(suffix)); +} + +static inline int find_mark(const char *mark, const char *string, int len, int *len_p) +{ + int mark_len = strlen(mark); + + if (mark_len <= len && + !strncasecmp(string + len - mark_len, mark, mark_len)) { + if (len_p) + *len_p -= mark_len; + return 1; + } + return 0; +} + static enum get_oid_result get_oid_1(struct repository *r, const char *name, int len, struct object_id *oid, unsigned lookup_flags); static int interpret_nth_prior_checkout(struct repository *r, const char *name, int namelen, struct strbuf *buf); @@ -811,6 +830,18 @@ static int get_oid_basic(struct repository *r, const char *str, int len, int refs_found = 0; int at, reflog_len, nth_prior = 0; + if (find_mark("@{hash}", str, len, &len)) { + struct strbuf sb = STRBUF_INIT; + + strbuf_add(&sb, str, len); + if (!get_oid_hex(sb.buf, oid) || + !get_short_oid(r, sb.buf, sb.len, oid, flags)) { + strbuf_release(&sb); + return 0; + } + die("Not a hash. Yes I know this should be fatal"); + } + if (len == r->hash_algo->hexsz && !get_oid_hex(str, oid)) { if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) { refs_found = repo_dwim_ref(r, str, len, &tmp_oid, &real_ref); @@ -837,7 +868,8 @@ static int get_oid_basic(struct repository *r, const char *str, int len, continue; } if (!upstream_mark(str + at, len - at) && - !push_mark(str + at, len - at)) { + !push_mark(str + at, len - at) && + !literal_mark(str + at, len - at)) { reflog_len = (len-1) - (at+2); len = at; } @@ -862,7 +894,14 @@ static int get_oid_basic(struct repository *r, const char *str, int len, } } - if (!len && reflog_len) + if (find_mark("@{literal}", str, len, &len)) { + if (reflog_len) + refs_found = repo_dwim_log_strict(r, str, len, oid, &real_ref); + else + refs_found = repo_dwim_ref_strict(r, str, len, oid, &real_ref); + if (!refs_found) + die("bad ref"); + } else if (!len && reflog_len) /* allow "@{...}" to mean the current branch reflog */ refs_found = repo_dwim_ref(r, "HEAD", 4, oid, &real_ref); else if (reflog_len) @@ -1180,6 +1219,11 @@ static enum get_oid_result get_oid_1(struct repository *r, if (!ret) return FOUND; + if (find_mark("@{describe}", name, len, &len)) { + ret = get_describe_name(r, name, len, oid); + return !ret ? FOUND : MISSING_OBJECT; + } + ret = get_oid_basic(r, name, len, oid, lookup_flags); if (!ret) return FOUND;
[I feel like this is something we should do, but I'm not sure. Hence RFC. The patch is mostly to play with if you're curious. The die() thing there is definitely wrong. And yeah all the syntax names are placeholders.] get_oid() is flexible and accepts multiple SHA-1 sources. Sometimes this flexibility is actually unwanted, especially for scripts. Let's talk problems: - Ambiguity aside, a script may want to check if branch A exists. Of course "git rev-parse A" won't cut it. But even "git rev-parse refs/heads/A" may fail: if you have refs/heads/refs/heads/A for whatever reason and the real branch "A" does not exist, the rev-parse rules allow to expand "refs/heads/A" to the long ref. - And then there's problem with using the wrong rule. 9309ba may look like a short hash. But if such short hash does not match any object, and there is refs/heads/9309ba, you'll have a little surprise. - The same for blahblah-g9309ba which could either be expanded to refs/heads/blahblah-g9309ba, or interpreted as git-describe output. - Ambiguation will also cause problems, but I don't think we need to get into that. Ambiguation may be addressed separately actually. There could be existing mitigation (e.g. maybe you can resolve blahblah-g9309ba and see if it's a ref or not). But it feels like we work around the problem than addressing it. The problem is we try every possible way to resolve a rev. Let's have some annotation to express that we only want to resolve a rev in a certain way: - <hash>@{hash} only accepts a full hash or a short hash. If it's a short hash, it cannot be ambiguous. - <ref>@{literal} only accepts full ref. No turning "master" into "refs/heads/master". - <output>@{describe} interprets <output> as git-describe output only, not an object name or a reference. This gives scripts much better control over get_oid(), which translates to rev-parse and a bunch other commands. PS. The new syntax can stack with existing ones. E.g. you could write refs/heads/master@{literal}@{yesterday} or <hash>@{hash}^{tree}. Perhaps I should allow these tags at the end too, so you can enforce a variable like "$REV"@{literal} where $REV could be even HEAD~123 Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> --- Documentation/revisions.txt | 10 ++++++++ refs.c | 41 +++++++++++++++++++++++++++++-- refs.h | 2 ++ sha1-name.c | 48 +++++++++++++++++++++++++++++++++++-- 4 files changed, 97 insertions(+), 4 deletions(-)