When the `--fork-point` argument was added to `git rebase`, we changed
the value of $upstream to be the fork point instead of the point from
which we want to rebase.  When $orig_head..$upstream is empty this does
not change the behaviour, but when there are new changes in the upstream
we are no longer checking if any of them are patch-identical with
changes in $upstream..$orig_head.
Fix this by introducing a new variable to hold the fork point and using
this to restrict the range as an extra (negative) revision argument so
that the set of desired revisions becomes (in fork-point mode):
	git rev-list --cherry-pick --right-only \
		$upstream...$orig_head ^$fork_point
This allows us to correctly handle the scenario where we have the
following topology:
	    C --- D --- E  <- dev
	   /
	  B  <- master@{1}
	 /
	o --- B' --- C* --- D*  <- master
where:
- B' is a fixed-up version of B that is not patch-identical with B;
- C* and D* are patch-identical to C and D respectively and conflict
  textually if applied in the wrong order;
- E depends textually on D.
The correct result of `git rebase master dev` is that B is identified as
the fork-point of dev and master, so that C, D, E are the commits that
need to be replayed onto master; but C and D are patch-identical with C*
and D* and so can be dropped, so that the end result is:
	o --- B' --- C* --- D* --- E  <- dev
If the fork-point is not identified, then picking B onto a branch
containing B' results in a conflict and if the patch-identical commits
are not correctly identified then picking C onto a branch containing D
(or equivalently D*) results in a conflict.
This change allows us to handle both of these cases, where previously we
either identified the fork-point (with `--fork-point`) but not the
patch-identical commits *or* (with `--no-fork-point`) identified the
patch-identical commits but not the fact that master had been rewritten.
Reported-by: Ted Felix <ted@tedfelix.com>
Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
		
	
		
			
				
	
	
		
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			102 lines
		
	
	
		
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# This shell script fragment is sourced by git-rebase to implement
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# its default, fast, patch-based, non-interactive mode.
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#
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# Copyright (c) 2010 Junio C Hamano.
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#
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# The whole contents of this file is run by dot-sourcing it from
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# inside a shell function.  It used to be that "return"s we see
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# below were not inside any function, and expected to return
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# to the function that dot-sourced us.
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#
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# However, FreeBSD /bin/sh misbehaves on such a construct and
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# continues to run the statements that follow such a "return".
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# As a work-around, we introduce an extra layer of a function
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# here, and immediately call it after defining it.
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git_rebase__am () {
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case "$action" in
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continue)
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	git am --resolved --resolvemsg="$resolvemsg" \
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		${gpg_sign_opt:+"$gpg_sign_opt"} &&
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	move_to_original_branch
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	return
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	;;
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skip)
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	git am --skip --resolvemsg="$resolvemsg" &&
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	move_to_original_branch
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	return
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	;;
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esac
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if test -z "$rebase_root"
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	# this is now equivalent to ! -z "$upstream"
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then
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	revisions=$upstream...$orig_head
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else
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	revisions=$onto...$orig_head
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fi
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ret=0
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if test -n "$keep_empty"
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then
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	# we have to do this the hard way.  git format-patch completely squashes
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	# empty commits and even if it didn't the format doesn't really lend
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	# itself well to recording empty patches.  fortunately, cherry-pick
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	# makes this easy
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	git cherry-pick ${gpg_sign_opt:+"$gpg_sign_opt"} --allow-empty \
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		--right-only "$revisions" \
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		${restrict_revision+^$restrict_revision}
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	ret=$?
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else
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	rm -f "$GIT_DIR/rebased-patches"
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	git format-patch -k --stdout --full-index --cherry-pick --right-only \
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		--src-prefix=a/ --dst-prefix=b/ --no-renames --no-cover-letter \
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		"$revisions" ${restrict_revision+^$restrict_revision} \
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		>"$GIT_DIR/rebased-patches"
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	ret=$?
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	if test 0 != $ret
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	then
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		rm -f "$GIT_DIR/rebased-patches"
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		case "$head_name" in
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		refs/heads/*)
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			git checkout -q "$head_name"
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			;;
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		*)
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			git checkout -q "$orig_head"
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			;;
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		esac
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		cat >&2 <<-EOF
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		git encountered an error while preparing the patches to replay
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		these revisions:
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		    $revisions
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		As a result, git cannot rebase them.
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		EOF
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		return $?
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	fi
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	git am $git_am_opt --rebasing --resolvemsg="$resolvemsg" \
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		${gpg_sign_opt:+"$gpg_sign_opt"} <"$GIT_DIR/rebased-patches"
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	ret=$?
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	rm -f "$GIT_DIR/rebased-patches"
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fi
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if test 0 != $ret
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then
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	test -d "$state_dir" && write_basic_state
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	return $ret
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fi
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move_to_original_branch
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}
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# ... and then we call the whole thing.
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git_rebase__am
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