blame,cat-file: Demonstrate --textconv is wrongly running converter on symlinks

git blame --textconv is wrongly calling the textconv filter on
symlinks: symlinks are stored as blobs whose content is the target of
the link, and blame calls the textconv filter on a temporary file
filled-in with the content of this blob.

For example:

    $ git blame -C -C regular-file.pdf
    Error: May not be a PDF file (continuing anyway)
    Error: PDF file is damaged - attempting to reconstruct xref table...
    Error: Couldn't find trailer dictionary
    Error: Couldn't read xref table
    Warning: program returned non-zero exit code #1
    fatal: unable to read files to diff

That errors come from pdftotext run on symlink.pdf being extracted to
/tmp/ with one-line plain-text content pointing to link destination.

So several failures are demonstrated here:

  - git cat-file --textconv :symlink.bin    # also HEAD:symlink.bin
  - git blame --textconv symlink.bin
  - git blame -C -C --textconv regular-file # but also looks on symlink.bin

At present they all fail with something like.

    E: /tmp/j3ELEs_symlink.bin is not "binary" file

NOTE: git diff doesn't try to textconv the pathnames, it runs the
textual diff without textconv, which is the expected behavior.

Signed-off-by: Kirill Smelkov <kirr@landau.phys.spbu.ru>
Reviewed-by: Matthieu Moy <Matthieu.Moy@grenoble-inp.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t8006-blame-textconv.sh

@@ -17,10 +17,16 @@ chmod +x helper
 test_expect_success 'setup ' '
 	echo "bin: test 1" >one.bin &&
 	echo "bin: test number 2" >two.bin &&
+	if test_have_prereq SYMLINKS; then
+		ln -s one.bin symlink.bin
+	fi &&
 	git add . &&
 	GIT_AUTHOR_NAME=Number1 git commit -a -m First --date="2010-01-01 18:00:00" &&
 	echo "bin: test 1 version 2" >one.bin &&
 	echo "bin: test number 2 version 2" >>two.bin &&
+	if test_have_prereq SYMLINKS; then
+		ln -sf two.bin symlink.bin
+	fi &&
 	GIT_AUTHOR_NAME=Number2 git commit -a -m Second --date="2010-01-01 20:00:00"
 '
 
@@ -78,4 +84,47 @@ test_expect_success 'blame from previous revision' '
 	test_cmp expected result
 '
 
+cat >expected <<EOF
+(Number2 2010-01-01 20:00:00 +0000 1) two.bin
+EOF
+
+test_expect_success SYMLINKS 'blame with --no-textconv (on symlink)' '
+	git blame --no-textconv symlink.bin >blame &&
+	find_blame <blame >result &&
+	test_cmp expected result
+'
+
+# fails with '...symlink.bin is not "binary" file'
+test_expect_failure SYMLINKS 'blame --textconv (on symlink)' '
+	git blame --textconv symlink.bin >blame &&
+	find_blame <blame >result &&
+	test_cmp expected result
+'
+
+# cp two.bin three.bin  and make small tweak
+# (this will direct blame -C -C three.bin to consider two.bin and symlink.bin)
+test_expect_success SYMLINKS 'make another new commit' '
+	cat >three.bin <<\EOF &&
+bin: test number 2
+bin: test number 2 version 2
+bin: test number 2 version 3
+bin: test number 3
+EOF
+	git add three.bin &&
+	GIT_AUTHOR_NAME=Number4 git commit -a -m Fourth --date="2010-01-01 23:00:00"
+'
+
+# fails with '...symlink.bin is not "binary" file'
+test_expect_failure SYMLINKS 'blame on last commit (-C -C, symlink)' '
+	git blame -C -C three.bin >blame &&
+	find_blame <blame >result &&
+	cat >expected <<\EOF &&
+(Number1 2010-01-01 18:00:00 +0000 1) converted: test number 2
+(Number2 2010-01-01 20:00:00 +0000 2) converted: test number 2 version 2
+(Number3 2010-01-01 22:00:00 +0000 3) converted: test number 2 version 3
+(Number4 2010-01-01 23:00:00 +0000 4) converted: test number 3
+EOF
+	test_cmp expected result
+'
+
 test_done

t/t8007-cat-file-textconv.sh

@@ -12,6 +12,9 @@ chmod +x helper
 
 test_expect_success 'setup ' '
 	echo "bin: test" >one.bin &&
+	if test_have_prereq SYMLINKS; then
+		ln -s one.bin symlink.bin
+	fi &&
 	git add . &&
 	GIT_AUTHOR_NAME=Number1 git commit -a -m First --date="2010-01-01 18:00:00" &&
 	echo "bin: test version 2" >one.bin &&
@@ -68,4 +71,30 @@ test_expect_success 'cat-file --textconv on previous commit' '
 	git cat-file --textconv HEAD^:one.bin >result &&
 	test_cmp expected result
 '
+
+test_expect_success SYMLINKS 'cat-file without --textconv (symlink)' '
+	git cat-file blob :symlink.bin >result &&
+	printf "%s" "one.bin" >expected
+	test_cmp expected result
+'
+
+
+# fails because cat-file tries to run converter on symlink.bin
+test_expect_failure SYMLINKS 'cat-file --textconv on index (symlink)' '
+	! git cat-file --textconv :symlink.bin 2>result &&
+	cat >expected <<\EOF &&
+fatal: git cat-file --textconv: unable to run textconv on :symlink.bin
+EOF
+	test_cmp expected result
+'
+
+# fails because cat-file tries to run converter on symlink.bin
+test_expect_failure SYMLINKS 'cat-file --textconv on HEAD (symlink)' '
+	! git cat-file --textconv HEAD:symlink.bin 2>result &&
+	cat >expected <<EOF &&
+fatal: git cat-file --textconv: unable to run textconv on HEAD:symlink.bin
+EOF
+	test_cmp expected result
+'
+
 test_done