Merge branch 'je/doc-push-upstream'

Documentation updates.

* je/doc-push-upstream:
  doc: git-push: add explanation of `git push origin main`
  doc: git-push: clarify "what to push"
  doc: git-push: clarify "where to push"
  doc: add an UPSTREAM BRANCHES section to pull/push/fetch
  doc: git-push: clarify intro

Author: gitster

Documentation/git-push.adoc

@@ -19,30 +19,35 @@ SYNOPSIS
 DESCRIPTION
 -----------
 
-Updates remote refs using local refs, while sending objects
-necessary to complete the given refs.
+Updates one or more branches, tags, or other references in a remote
+repository from your local repository, and sends all necessary data
+that isn't already on the remote.
 
-You can make interesting things happen to a repository
-every time you push into it, by setting up 'hooks' there.  See
-documentation for linkgit:git-receive-pack[1].
+The simplest way to push is `git push <remote> <branch>`.
+`git push origin main` will push the local `main` branch to the `main`
+branch on the remote named `origin`.
+
+The `<repository>` argument defaults to the upstream for the current branch,
+or `origin` if there's no configured upstream.
 
-When the command line does not specify where to push with the
-`<repository>` argument, `branch.*.remote` configuration for the
-current branch is consulted to determine where to push.  If the
-configuration is missing, it defaults to 'origin'.
+To decide which branches, tags, or other refs to push, Git uses
+(in order of precedence):
 
-When the command line does not specify what to push with `<refspec>...`
-arguments or `--all`, `--mirror`, `--tags` options, the command finds
-the default `<refspec>` by consulting `remote.*.push` configuration,
-and if it is not found, honors `push.default` configuration to decide
-what to push (See linkgit:git-config[1] for the meaning of `push.default`).
+1. The `<refspec>` argument(s) (for example `main` in `git push origin main`)
+   or the `--all`, `--mirror`, or `--tags` options
+2. The `remote.*.push` configuration for the repository being pushed to
+3. The `push.default` configuration. The default is `push.default=simple`,
+   which will push to a branch with the same name as the current branch.
+   See the <<CONFIGURATION,CONFIGURATION>> section below for more on `push.default`.
 
-When neither the command-line nor the configuration specifies what to
-push, the default behavior is used, which corresponds to the `simple`
-value for `push.default`: the current branch is pushed to the
-corresponding upstream branch, but as a safety measure, the push is
-aborted if the upstream branch does not have the same name as the
-local one.
+`git push` may fail if you haven't set an upstream for the current branch,
+depending on what `push.default` is set to.
+See the <<UPSTREAM-BRANCHES,UPSTREAM BRANCHES>> section below for more
+on how to set and use upstreams.
+
+You can make interesting things happen to a repository
+every time you push into it, by setting up 'hooks' there.  See
+documentation for linkgit:git-receive-pack[1].
 
 
 OPTIONS[[OPTIONS]]
@@ -710,6 +715,7 @@ a `git gc` command on the origin repository.
 
 include::transfer-data-leaks.adoc[]
 
+[[CONFIGURATION]]
 CONFIGURATION
 -------------
 

Documentation/urls-remotes.adoc

@@ -92,5 +92,47 @@ git push uses:
 ------------
 
 
+[[UPSTREAM-BRANCHES]]
+UPSTREAM BRANCHES
+-----------------
+
+Branches in Git can optionally have an upstream remote branch.
+Git defaults to using the upstream branch for remote operations, for example:
+
+* It's the default for `git pull` or `git fetch` with no arguments.
+* It's the default for `git push` with no arguments, with some exceptions.
+  For example, you can use the `branch.<name>.pushRemote` option to push
+  to a different remote than you pull from, and by default with
+  `push.default=simple` the upstream branch you configure must have
+  the same name.
+* Various commands, including `git checkout` and `git status`, will
+  show you how many commits have been added to your current branch and
+  the upstream since you forked from it, for example "Your branch and
+  'origin/main' have diverged, and have 2 and 3 different commits each
+  respectively".
+
+The upstream is stored in `.git/config`, in the "remote" and "merge"
+fields. For example, if `main`'s upstream is `origin/main`:
 
+------------
+[branch "main"]
+   remote = origin
+   merge = refs/heads/main
+------------
 
+You can set an upstream branch explicitly with
+`git push --set-upstream <remote> <branch>`
+but Git will often automatically set the upstream for you, for example:
+
+* When you clone a repository, Git will automatically set the upstream
+  for the default branch.
+* If you have the `push.autoSetupRemote` configuration option set,
+  `git push` will automatically set the upstream the first time you push
+  a branch.
+* Checking out a remote-tracking branch with `git checkout <branch>`
+  will automatically create a local branch with that name and set
+  the upstream to the remote branch.
+
+[NOTE]
+Upstream branches are sometimes referred to as "tracking information",
+as in "set the branch's tracking information".