From: Junio C Hamano <gitster@pobox.com>
To: Kevin Bracey <kevin@bracey.fi>
Cc: git@vger.kernel.org, David Aguilar <davvid@gmail.com>,
Ciaran Jessup <ciaranj@gmail.com>,
Scott Chacon <schacon@gmail.com>,
Alex Riesen <raa.lkml@gmail.com>
Subject: Re: [PATCH v2 2/3] mergetools/p4merge: create a base if none available
Date: Sat, 09 Mar 2013 20:55:55 -0800 [thread overview]
Message-ID: <7v7glfetus.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <1362856860-15205-3-git-send-email-kevin@bracey.fi> (Kevin Bracey's message of "Sat, 9 Mar 2013 21:20:59 +0200")
Kevin Bracey <kevin@bracey.fi> writes:
> diff --git a/git-sh-setup.sh b/git-sh-setup.sh
> index 795edd2..aa9a732 100644
> --- a/git-sh-setup.sh
> +++ b/git-sh-setup.sh
> @@ -249,6 +249,19 @@ clear_local_git_env() {
> unset $(git rev-parse --local-env-vars)
> }
>
> +# Generate a virtual base file for a two-file merge. On entry the
> +# base file $1 should be a copy of $2. Uses git apply to remove
> +# lines from $1 that are not in $3, leaving only common lines.
> +create_virtual_base() {
> + sz0=$(wc -c <"$1")
> + @@DIFF@@ -u -La/"$1" -Lb/"$1" "$2" "$3" | git apply --no-add
> + sz1=$(wc -c <"$1")
> +
> + # If we do not have enough common material, it is not
> + # worth trying two-file merge using common subsections.
> + expr $sz0 \< $sz1 \* 2 >/dev/null || : >"$1"
> +}
> +
This rewrite is wrong. It should be
> + sz0=$(wc -c <"$1")
> + @@DIFF@@ -u -La/"$1" -Lb/"$1" "$1" "$3" | git apply --no-add
> + sz1=$(wc -c <"$1")
for it to make sense. "diff $1 $3" is a change to go from $1 to $3;
with "-La/$1 -Lb/$1", we declare that the change is to be applied to
$1, and use --no-add to only use the removal from the diff when we
edit $1 using this mechanism.
The end effect is to in-place edit "$1" to remove what is not common
with "$3", and sz0/sz1 computation is done on "$1" for this reason.
Does it (i.e. "$1") shrink sufficiently when we remove the material
that is not common in it (i.e. "$1") and "$3"?
This part is a two-file operation between $1 and $3; there is
nothing you would want to pass $2 to influence what the above three
lines do.
It may happen that the caller has two copies of the same thing,
$orig and $src1, and uses one for $1 and the other for $2, so you
won't observe the damage from the incorrect rewriting of the above
logic, but it invites the next caller to incorrectly feed something
totally unrelated to $1 and $2.
Please fix it to a function that takes two temporary paths, not
three.
next prev parent reply other threads:[~2013-03-10 4:56 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-06 20:32 [PATCH 0/2] Improve P4Merge mergetool invocation Kevin Bracey
2013-03-06 20:32 ` [PATCH 1/2] p4merge: swap LOCAL and REMOTE for mergetool Kevin Bracey
2013-03-07 0:36 ` Junio C Hamano
2013-03-07 6:16 ` Kevin Bracey
2013-03-07 7:23 ` Junio C Hamano
2013-03-07 17:14 ` Kevin Bracey
2013-03-07 19:10 ` Junio C Hamano
2013-03-07 19:50 ` David Aguilar
2013-03-07 20:31 ` Junio C Hamano
2013-03-06 20:32 ` [PATCH 2/2] p4merge: create a virtual base if none available Kevin Bracey
2013-03-07 2:23 ` David Aguilar
2013-03-07 6:28 ` Kevin Bracey
2013-03-07 7:25 ` Junio C Hamano
2013-03-07 3:33 ` David Aguilar
2013-03-09 19:20 ` [PATCH v2 0/3] Improve P4Merge mergetool invocation Kevin Bracey
2013-03-09 19:20 ` [PATCH v2 1/3] mergetools/p4merge: swap LOCAL and REMOTE Kevin Bracey
2013-03-09 19:20 ` [PATCH v2 2/3] mergetools/p4merge: create a base if none available Kevin Bracey
2013-03-10 4:55 ` Junio C Hamano [this message]
2013-03-09 19:21 ` [PATCH v2 3/3] git-merge-one-file: revise merge error reporting Kevin Bracey
2013-03-13 1:12 ` [PATCH v3 1/3] mergetools/p4merge: swap LOCAL and REMOTE Kevin Bracey
2013-03-13 1:12 ` [PATCH v3 2/3] mergetools/p4merge: create a base if none available Kevin Bracey
2013-03-13 1:12 ` [PATCH v3 3/3] git-merge-one-file: revise merge error reporting Kevin Bracey
2013-03-13 9:03 ` David Aguilar
2013-03-24 12:26 ` [PATCH v2 0/3] git-merge-one-file " Kevin Bracey
2013-03-24 12:26 ` [PATCH v2 1/3] git-merge-one-file: style cleanup Kevin Bracey
2013-03-24 12:26 ` [PATCH v2 2/3] git-merge-one-file: send "ERROR:" messages to stderr Kevin Bracey
2013-03-24 12:26 ` [PATCH v2 3/3] git-merge-one-file: revise merge error reporting Kevin Bracey
2013-03-25 17:04 ` Junio C Hamano
2013-03-25 17:17 ` Junio C Hamano
2013-03-25 17:20 ` Junio C Hamano
2013-03-25 19:24 ` Eric Sunshine
2013-03-13 17:57 ` [PATCH v3 " Junio C Hamano
2013-03-14 6:27 ` Kevin Bracey
2013-03-14 14:56 ` Junio C Hamano
2013-03-14 17:31 ` Kevin Bracey
2013-03-14 17:39 ` Kevin Bracey
2013-03-13 2:05 ` [PATCH v3 1/3] mergetools/p4merge: swap LOCAL and REMOTE David Aguilar
2013-03-24 11:54 ` [PATCH v4 1/2] " Kevin Bracey
2013-03-24 11:54 ` [PATCH v4 2/2] mergetools/p4merge: create a base if none available Kevin Bracey
2013-03-25 17:47 ` Junio C Hamano
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