Make git add -i work

[dmik]

Currently it fails with:

Cannot close git rev-parse --git-dir (No children) at D:/Coding/git/master-run/libexec/git-core/git-add--interactive line 187.

This is new (brought by 2.30.2) and appears to be due to this change in git-add--interactive.perl:

Apparently, closing a pipe fails with error on OS/2.

Also, even if I work around this, it fails earlier when staging individual chunks like this:

(1/1) Stage this hunk [y,n,q,a,d,e,?]? y
error: patch failed: test.txt:1
                               error: test.txt: patch does not apply
                                                                    diff --git a/test.txt b/test.txt
index 8a66d40..4122eca 100644
--- a/test.txt
+++ b/test.txt
@@ -1 +1,3 @@
-wef
\ No newline at end of file
+wef
+this line to add now
+this line to add later

Perhaps, some CRLF issue as usual (both when applying patches and when outputting messages to the console).

[dmik]

The second failure when applying the patch seems to also be related to how perl processes piped commands. There is this piece of code in git-apply--interactive.perl:

sub run_git_apply {
	my $cmd = shift;
	my $fh;
	open $fh, '| git ' . $cmd . " --allow-overlap";
	print $fh @_;
	return close $fh;
}

$cmd in our case is apply --cached. What this code does is opens a piped command (starts git apply --cached in a child process with connected standard input and output) and then feeds it with the normal patch file. If I also add -v to the command, then I see this output:

Checking patch test.txt...
                          error: while searching for:
                                                     wef?
                                                           error: patch failed: test.txt:1
                                                                                          error: test.txt: patch does not apply
diff --git a/test.txt b/test.txt
index 8a66d40..4122eca 100644
--- a/test.txt
+++ b/test.txt
@@ -1 +1,3 @@
-wef
\ No newline at end of file
+wef
+this line to add now
+this line to add later

I.e. git apply complains that it can't find wef? in the source file. While the patch file clearly says it should search for wef (no question mark at the end). Note that if I try to apply the patch directly (by saving it to a file), it works like a charm (no matter what EOLs the patch file has).

My current guess is that it's also a Perl issue. Perhaps, perl translates EOL to some non-printable character and git prints it as ? in the verbose output... Needs checking.

[dmik]

The second problem appears to be in Perl as well, see bitwiseworks/perl-os2#1 (comment). In short, when Perl pipes a patch file to git apply, it performs LF -> CRLF translation and that breaks git apply because it never expects CRLF when reading a patch (and can't match the strings because of an extra CR at the end). It's a question whether should we need to fix Git itself or not — first we need to sort out the Perl issue.