Git for Windows crash when I try to use git difftool -d on a file added with -N option

[sachinrk]

• I was not able to find an open or closed issue matching what I'm seeing

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit?
  git version 2.27.0.windows.1
  64 bit.

I recently upgraded the git version, but the issue was reproducible on older versions as well.

$ git --version --build-options

git version 2.27.0.windows.1
cpu: x86_64
built from commit: 907ab1011dce9112700498e034b974ba60f8b407
sizeof-long: 4
sizeof-size_t: 8

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

$ cmd.exe /c ver

Microsoft Windows [Version 10.0.18363.836

• What options did you set as part of the installation? Or did you choose the
  defaults?

# One of the following:
> type "C:\Program Files\Git\etc\install-options.txt"
> type "C:\Program Files (x86)\Git\etc\install-options.txt"
> type "%USERPROFILE%\AppData\Local\Programs\Git\etc\install-options.txt"
$ cat /etc/install-options.txt

type "C:\Program Files\Git\etc\install-options.txt"

Editor Option: VIM
Custom Editor Path:
Path Option: Cmd
SSH Option: OpenSSH
Tortoise Option: false
CURL Option: OpenSSL
CRLF Option: CRLFAlways
Bash Terminal Option: MinTTY
Git Pull Behavior Option: Merge
Performance Tweaks FSCache: Enabled
Use Credential Manager: Enabled
Enable Symlinks: Disabled
Enable Pseudo Console Support: Disabled

• Any other interesting things about your environment that might be related
  to the issue you're seeing?

Nothing interesting.

Details

• Which terminal/shell are you running Git from? e.g Bash/CMD/PowerShell/other

CMD

• What commands did you run to trigger this issue? If you can provide a
  Minimal, Complete, and Verifiable example
  this will help us understand the issue.

In a new branch, simply 
notepad++ a.txt
git add -N a.txt
git difftool -d

• What did you expect to occur after running these commands?

No crash, and that git would open my difftool with the diff of the file

• What actually happened instead?

d:\RoutingPlane\sources\dev\CAFE\NanoProxy>git difftool -d
error: unable to read sha1 file of C:\Users\sakul\AppData\Local\Temp\git-difftool.a32148/right/build/configuration/public/xml/a.txt (4b825dc642cb6eb9a060e54bf8d69288fbee4904)
error: could not write 'build/configuration/public/xml/a.txt'

Crash dialog saying Git for Windows has stopped working

• If the problem was occurring with a specific repository, can you provide the
  URL to that repository to help us with testing?

Not specific to the repository

[dscho]

I can reproduce, even on Linux (read: this problem is not Windows-specific):

diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index e66af3682f8..731ed73f421 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -720,6 +720,14 @@ test_expect_success SYMLINKS 'difftool --dir-diff handles modified symlinks' '
 	test_cmp expect actual
 '
 
+test_expect_success 'add -N and difftool -d' '
+	test_when_finished git reset --hard &&
+
+	test_write_lines A B C >intent-to-add &&
+	git add -N intent-to-add &&
+	git difftool --dir-diff --extcmd ls
+'
+
 test_expect_success 'outside worktree' '
 	echo 1 >1 &&
 	echo 2 >2 &&

And this seems to fix it:

diff --git a/diff.c b/diff.c
index d1ad6a3c4ad..3503dcdf0db 100644
--- a/diff.c
+++ b/diff.c
@@ -5684,6 +5684,9 @@ static void diff_flush_raw(struct diff_filepair *p, struct diff_options *opt)
 	int line_termination = opt->line_termination;
 	int inter_name_termination = line_termination ? '\t' : '\0';
 
+	diff_fill_oid_info(p->one, opt->repo->index);
+	diff_fill_oid_info(p->two, opt->repo->index);
+
 	fprintf(opt->file, "%s", diff_line_prefix(opt));
 	if (!(opt->output_format & DIFF_FORMAT_NAME_STATUS)) {
 		fprintf(opt->file, ":%06o %06o %s ", p->one->mode, p->two->mode,

[sachinrk]

I can reproduce, even on Linux (read: this problem is not Windows-specific):

diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index e66af3682f8..731ed73f421 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -720,6 +720,14 @@ test_expect_success SYMLINKS 'difftool --dir-diff handles modified symlinks' '
 	test_cmp expect actual
 '
 
+test_expect_success 'add -N and difftool -d' '
+	test_when_finished git reset --hard &&
+
+	test_write_lines A B C >intent-to-add &&
+	git add -N intent-to-add &&
+	git difftool --dir-diff --extcmd ls
+'
+
 test_expect_success 'outside worktree' '
 	echo 1 >1 &&
 	echo 2 >2 &&

And this seems to fix it:

diff --git a/diff.c b/diff.c
index d1ad6a3c4ad..3503dcdf0db 100644
--- a/diff.c
+++ b/diff.c
@@ -5684,6 +5684,9 @@ static void diff_flush_raw(struct diff_filepair *p, struct diff_options *opt)
 	int line_termination = opt->line_termination;
 	int inter_name_termination = line_termination ? '\t' : '\0';
 
+	diff_fill_oid_info(p->one, opt->repo->index);
+	diff_fill_oid_info(p->two, opt->repo->index);
+
 	fprintf(opt->file, "%s", diff_line_prefix(opt));
 	if (!(opt->output_format & DIFF_FORMAT_NAME_STATUS)) {
 		fprintf(opt->file, ":%06o %06o %s ", p->one->mode, p->two->mode,

Thanks for the quick fix! :)

[dscho]

It's not actually a fix because it fails the test suite, pointing out a rather big conceptual problem (I did not figure out how to distinguish between a cache_entry that is --intent-to-add vs one that is simply in need of refreshing).