From: Julia Evans Date: Tue, 23 Sep 2025 18:10:48 +0000 (+0000) Subject: doc: git-push: create PUSH RULES section X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=cc1cc31e2a46e33941840bbb2026fff2d0532b2b;p=thirdparty%2Fgit.git doc: git-push: create PUSH RULES section Right now the rules for when a `git push` is allowed are buried at the bottom of the description of ``. Put them in their own section so that we can reference them from `--force` and give some context for why they exist. Having the "PUSH RULES" section also lets us be a little bit more specific with the rule in `--force`: we can just focus on the rule for pushing for a branch (which is likely the one that's most relevant) and leave the details about what happens when you push to a tag or a ref that isn't a branch to the later section. Signed-off-by: Julia Evans Signed-off-by: Junio C Hamano --- diff --git a/Documentation/git-push.adoc b/Documentation/git-push.adoc index 5f5408e2c0..cf506ab8b4 100644 --- a/Documentation/git-push.adoc +++ b/Documentation/git-push.adoc @@ -91,48 +91,6 @@ is ambiguous. configuration (see linkgit:git-config[1]) suggest what refs/ namespace you may have wanted to push to. --- -+ -The object referenced by is used to update the reference -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. -+ -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 @@ -145,6 +103,7 @@ the local side, the remote side is updated if a branch of the same name already exists on the remote side. + `tag ` means the same as `refs/tags/:refs/tags/`. +Not all updates are allowed: see PUSH RULES below for the details. --all:: --branches:: @@ -335,14 +294,12 @@ allowing a forced update. -f:: --force:: - Usually, the command refuses to update a remote ref that is - not an ancestor of the local ref used to overwrite it. - Also, when `--force-with-lease` option is used, the command refuses - to update a remote ref whose current value does not match - what is expected. + Usually, `git push` will refuse to update a branch that is not an + ancestor of the commit being pushed. + -This flag disables these checks, and can cause the remote repository -to lose commits; use it with care. +This flag disables that check, the other safety checks in PUSH RULES +below, and the checks in --force-with-lease. It can cause the remote +repository to lose commits; use it with care. + Note that `--force` applies to all the refs that are pushed, hence using it with `push.default` set to `matching` or with multiple push @@ -514,6 +471,45 @@ reason:: refs, no explanation is needed. For a failed ref, the reason for failure is described. +PUSH RULES +---------- + +As a safety feature, the `git push` command only allows certain kinds of +updates to prevent you from accidentally losing data on the remote. + +Because branches and tags are intended to be used differently, the +safety rules for pushing to a branch are different from the rules +for pushing to a tag. In the following rules "update" means any +modifications except deletions and creations. Deletions and creations +are always allowed, except when forbidden by configuration or hooks. + +1. If the push destination is a **branch** (`refs/heads/*`): only + fast-forward updates are allowed, which means the destination must be + an ancestor of the source commit. The source must be a commit. +2. If the push destination is a **tag** (`refs/tags/*`): all updates will + be rejected. The source can be any object. +3. If the push destination is not a branch or tag: + * If the source is a tree or blob object, any updates will be rejected + * If the source is a tag or commit object, any fast-forward update + 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. + +You can override these rules by passing `--force` or by adding the +optional leading `+` to a refspec. The only exceptions are that no +amount of forcing will make a branch accept a non-commit object, +and forcing won't make the remote repository accept a push that it's +configured to deny. + +Hooks and configuration can also override or amend these rules, +see e.g. `receive.denyNonFastForwards` and `receive.denyDeletes` +in linkgit:git-config[1] and `pre-receive` and `update` in +linkgit:githooks[5]. + NOTE ABOUT FAST-FORWARDS ------------------------