Re: [PATCH v2] mergetools: add support for DeltaWalker

On Sat, Mar 3, 2012 at 7:50 PM, Tim Henigan [off-list ref] wrote:

On Sat, Mar 3, 2012 at 5:47 PM, Junio C Hamano [off-list ref] wrote:

quoted

David Aguilar [off-list ref] writes:

quoted

quoted

quoted

+merge_cmd () {
+     if $base_present
+     then
+             "$merge_tool_path" "$LOCAL" "$REMOTE" "$BASE" -merged="$PWD/$MERGED"
+     else
+             "$merge_tool_path" "$LOCAL" "$REMOTE" -merged="$PWD/$MERGED"
+     fi >/dev/null 2>&1
+}

Is the $PWD/ prefix strictly needed?  The rest of the mergetools use
$MERGED as-is.  Does it work without it?

Hrm, I didn't notice it but they do look fishy.  Thanks for good eyes.

Tim?

I ran a quick test using msysgit v1.7.9 on Win7 64-bit and found that
it fails without '$PWD'.

When '$PWD/' is removed from the '-merged' option, it results in a
Java JRE crash and the conflict resolutions entered by the user are
not written to the file.

The JRE exception is 'EXCEPTION_ACCESS_VIOLATION (0xc0000005)'.  I
posted the full text of the exception to a public location, in case
anyone is interested [1].

The format of the '-merged' option was copied directly from the
DeltaWalker manual.  There was no explanation why '$PWD' is needed.

[1]: https://gist.github.com/1970590

Thanks, that makes a lot of sense.  It looks like they have a bug.  Do
they know about it?

My naive guess is that they are using some inotify-like thing and
subscribing to a directory (per the stack trace).  Since
dirname("relative") is "" they crash.

So this bug probably wouldn't be present when merging a file in a
sub-directory, or ../ relative path.  Is this the case?

Can you mention this in a comment so that someone doesn't copy/paste
it into another tool in the future?

If they fix it then we may want to consider only supporting the newer
version and remove the $PWD.  Does the OS X version have this bug too?

I didn't notice any other production shell scripts in git using $PWD.
There is one use of `pwd` in git-stash.sh and it's used in a few
tests, as is $PWD, but $(pwd) is the most prevalent overall.  I don't
know the reason $PWD is avoided in the git shell scripts (though
portability is often the reason).

Deltawalker is not currently available on any of the platforms where
this would be a concern, but we may still want to use $(pwd) for
consistency with the other commands.  Does that work instead?
-- 
David