rebase: use @{upstream} if no upstream specified

'git rebase' without arguments is currently not supported. Make it
default to 'git rebase @{upstream}'. That is also what 'git pull
[--rebase]' defaults to, so it only makes sense that 'git rebase'
defaults to the same thing.

Defaulting to @{upstream} will make it possible to run e.g. 'git
rebase -i' without arguments, which is probably a quite common use
case. It also improves the scenario where you have multiple branches
that rebase against a remote-tracking branch, where you currently have
to choose between the extra network delay of 'git pull' or the
slightly awkward keys to enter 'git rebase @{u}'.

The error reporting when no upstream is configured for the current
branch or when no branch is checked out is reused from git-pull.sh. A
function is extracted into git-parse-remote.sh for this purpose.

Helped-by: Yann Dirson <ydirson@altern.org>
Helped-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Martin von Zweigbergk <martin.von.zweigbergk@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/git-parse-remote.sh b/git-parse-remote.sh
index 1cc2ba6e09..be17ecbd1e 100644
--- a/git-parse-remote.sh
+++ b/git-parse-remote.sh
@@ -99,3 +99,41 @@ get_remote_merge_branch () {
 	    esac
 	esac
 }
+
+error_on_missing_default_upstream () {
+	cmd="$1"
+	op_type="$2"
+	op_prep="$3"
+	example="$4"
+	branch_name=$(git symbolic-ref -q HEAD)
+	if test -z "$branch_name"
+	then
+		echo "You are not currently on a branch, so I cannot use any
+'branch.<branchname>.merge' in your configuration file.
+Please specify which branch you want to $op_type $op_prep on the command
+line and try again (e.g. '$example').
+See git-${cmd}(1) for details."
+	else
+		echo "You asked me to $cmd without telling me which branch you
+want to $op_type $op_prep, and 'branch.${branch_name#refs/heads/}.merge' in
+your configuration file does not tell me, either. Please
+specify which branch you want to use on the command line and
+try again (e.g. '$example').
+See git-${cmd}(1) for details.
+
+If you often $op_type $op_prep the same branch, you may want to
+use something like the following in your configuration file:
+    [branch \"${branch_name#refs/heads/}\"]
+    remote = <nickname>
+    merge = <remote-ref>"
+		test rebase = "$op_type" &&
+		echo "    rebase = true"
+		echo "
+    [remote \"<nickname>\"]
+    url = <url>
+    fetch = <refspec>
+
+See git-config(1) for details."
+	fi
+	exit 1
+}