From: Ævar Arnfjörð Bjarmason Date: Tue, 31 Jul 2018 13:07:14 GMT Subject: [PATCH v2 06/10] push doc: correct lies about how push refspecs work Message-ID: <20180731130718.25222-7-avarab@gmail.com> In-Reply-To: <20180429202100.32353-1-avarab@gmail.com> There's complex rules governing whether a push is allowed to take place depending on whether we're pushing to refs/heads/*, refs/tags/* or refs/not-that/*. See is_branch() in refs.c, and the various assertions in refs/files-backend.c. (e.g. "trying to write non-commit object %s to branch '%s'"). This documentation has never been quite correct, but went downhill after dbfeddb12e ("push: require force for refs under refs/tags/", 2012-11-29) when we started claiming that couldn't be a tag object, which is incorrect. After some of the logic in that patch was changed in 256b9d70a4 ("push: fix "refs/tags/ hierarchy cannot be updated without --force"", 2013-01-16) the docs weren't updated, and we've had some version of documentation that confused whether was a tag or not with whether would accept either an annotated tag object or the commit it points to. This makes the intro somewhat more verbose & complex, perhaps we should have a shorter description here and split the full complexity into a dedicated section. Very few users will find themselves needing to e.g. push blobs or trees to refs/custom-namespace/* (or blobs or trees at all), and that could be covered separately as an advanced topic. Signed-off-by: Ævar Arnfjörð Bjarmason --- Documentation/git-push.txt | 30 ++++++++++++++++++++++-------- Documentation/gitrevisions.txt | 7 ++++--- 2 files changed, 26 insertions(+), 11 deletions(-) diff --git a/Documentation/git-push.txt b/Documentation/git-push.txt index 55277a9781..fe654482dc 100644 --- a/Documentation/git-push.txt +++ b/Documentation/git-push.txt @@ -60,8 +60,9 @@ OPTIONS[[OPTIONS]] by a colon `:`, followed by the destination ref . + The is often the name of the branch you would want to push, but -it can be any arbitrary "SHA-1 expression", such as `master~4` or -`HEAD` (see linkgit:gitrevisions[7]). +it can be any arbitrary expression to a commit, such as `master~4` or +`HEAD` (see linkgit:gitrevisions[7]). It can also refer to tag +objects, trees or blobs if the is outside of `refs/heads/*`. + The tells which ref on the remote side is updated with this push. Arbitrary expressions cannot be used here, an actual ref must @@ -74,12 +75,25 @@ without any `` on the command line. Otherwise, missing `:` means to update the same ref as the ``. + The object referenced by is used to update the reference -on the remote side. By default this is only allowed if is not -a tag (annotated or lightweight), and then only if it can fast-forward -. By having the optional leading `+`, you can tell Git to update -the ref even if it is not allowed by default (e.g., it is not a -fast-forward.) This does *not* attempt to merge into . See -EXAMPLES below for details. +on the remote side. Whether this is allowed depends on where in +`refs/*` the reference lives. The `refs/heads/*` namespace will +only accept commit objects, and then only they can be +fast-forwarded. The `refs/tags/*` namespace will accept any kind of +object, and any changes to them and others types of objects will be +rejected. Finally, it's possible to push any type of object to any +namespace outside of `refs/{tags,heads}/*`, but these will be treated +as branches for the purposes of whether `--force` is required, even in +the case where a tag object is pushed. That tag object will be +overwritten by another tag object (or commit!) without `--force` if +the new tag happens to point to a commit that's a fast-forward of the +commit it replaces. ++ +By having the optional leading `+` to a refspec (or using `--force` +command line option) you can tell Git to update the ref even if +it is not allowed by its respective namespace clobbering rules (e.g., +it is not a fast-forward. in the case of `refs/heads/*` updates) This +does *not* attempt to merge into . See EXAMPLES below for +details. + `tag ` means the same as `refs/tags/:refs/tags/`. + diff --git a/Documentation/gitrevisions.txt b/Documentation/gitrevisions.txt index 1f6cceaefb..d407b7dee1 100644 --- a/Documentation/gitrevisions.txt +++ b/Documentation/gitrevisions.txt @@ -19,9 +19,10 @@ walk the revision graph (such as linkgit:git-log[1]), all commits which are reachable from that commit. For commands that walk the revision graph one can also specify a range of revisions explicitly. -In addition, some Git commands (such as linkgit:git-show[1]) also take -revision parameters which denote other objects than commits, e.g. blobs -("files") or trees ("directories of files"). +In addition, some Git commands (such as linkgit:git-show[1] and +linkgit:git-push[1]) can also take revision parameters which denote +other objects than commits, e.g. blobs ("files") or trees +("directories of files"). include::revisions.txt[] -- 2.18.0.345.g5c9ce644c3