From fe802bd21e81cceedff2db79cc3c9a5ad75b4f93 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= Date: Fri, 31 Aug 2018 20:10:02 +0000 Subject: [PATCH] push doc: correct lies about how push refspecs work MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Junio C Hamano --- Documentation/git-push.txt | 50 +++++++++++++++++++++++++++++----- Documentation/gitrevisions.txt | 7 +++-- 2 files changed, 47 insertions(+), 10 deletions(-) diff --git a/Documentation/git-push.txt b/Documentation/git-push.txt index 71c78ac1a4..f345bd30fc 100644 --- a/Documentation/git-push.txt +++ b/Documentation/git-push.txt @@ -74,14 +74,50 @@ 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.). +on the remote side. Whether this is allowed depends on where in +`refs/*` the reference lives as described in detail below, in +those sections "update" means any modifications except deletes, which +as noted after the next few sections are treated differently. + -Pushing an empty allows you to delete the ref from -the remote repository. +The `refs/heads/*` namespace will only accept commit objects, and +updates only if they can be fast-forwarded. ++ +The `refs/tags/*` namespace will accept any kind of object (as +commits, trees and blobs can be tagged), and any updates to them will +be rejected. ++ +It's possible to push any type of object to any namespace outside of +`refs/{tags,heads}/*`. In the case of tags and commits, these will be +treated as if they were the commits inside `refs/heads/*` for the +purposes of whether the update is allowed. ++ +I.e. a fast-forward of commits and tags outside `refs/{tags,heads}/*` +is allowed, even in cases where what's being fast-forwarded is not a +commit, but a tag object which happens to point to a new commit which +is a fast-forward of the commit the last tag (or commit) it's +replacing. Replacing a tag with an entirely different tag is also +allowed, if it points to the same commit, as well as pushing a peeled +tag, i.e. pushing the commit that existing tag object points to, or a +new tag object which an existing commit points to. ++ +Tree and blob objects outside of `refs/{tags,heads}/*` will be treated +the same way as if they were inside `refs/tags/*`, any update of them +will be rejected. ++ +All of the rules described above about what's not allowed as an update +can be overridden by adding an the optional leading `+` to a refspec +(or using `--force` command line option). The only exception to this +is that no amount of forcing will make the `refs/heads/*` namespace +accept a non-commit object. Hooks and configuration can also override +or amend these rules, see e.g. `receive.denyNonFastForwards` in +linkgit:git-config[1] and`pre-receive` and `update` in +linkgit:githooks[5]. ++ +Pushing an empty allows you to delete the ref from the +remote repository. Deletions are always accepted without a leading `+` +in the refspec (or `--force`), except when forbidden by configuration +or hooks. See `receive.denyDeletes` in linkgit:git-config[1] and +`pre-receive` and `update` in linkgit:githooks[5]. + The special refspec `:` (or `+:` to allow non-fast-forward updates) directs Git to push "matching" branches: for every branch that exists on 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[]