[PATCH 7/7] apply --allow-overlap: fix a corner case

From: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date: Dec 6, 2019, 13:08 UTC
Message-ID: <15c4cce5a027d56c7ddbe5523cf0f3beabd06ed7.1575637705.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.172.git.1575637705.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

Yes, yes, this is supposed to be only a band-aid option for `git add -p` not Doing The Right Thing. But as long as we carry the `--allow-overlap` option, we might just as well get it right.

This fixes the case where one hunk inserts a line before the first line, and is followed by a hunk whose context overlaps with the first one's and which appends a line at the end.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 apply.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/apply.c b/apply.c
index f8a046a6a5..720a631eaa 100644
--- a/apply.c
+++ b/apply.c
@@ -2661,6 +2661,16 @@ static int find_pos(struct apply_state *state,
 	unsigned long backwards, forwards, current;
 	int backwards_lno, forwards_lno, current_lno;
 
+	/*
+	 * When running with --allow-overlap, it is possible that a hunk is
+	 * seen that pretends to start at the beginning (but no longer does),
+	 * and that *still* needs to match the end. So trust `match_end` more
+	 * than `match_beginning`.
+	 */
+	if (state->allow_overlap && match_beginning && match_end &&
+	    img->nr - preimage->nr != 0)
+		match_beginning = 0;
+
 	/*
 	 * If match_beginning or match_end is specified, there is no
 	 * point starting from a wrong line that will never match and

-- 
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