t/t-credentials.sh: also test .netrc on Windows

In previous commits in this PR we revised the ParseNetrc() function
in our "creds" package to support both ".netrc" and "_netrc" files
on Windows, whereas it has previously only supported "_netrc" files.

This change will align the behaviour of the Git LFS client with that
of contemporary versions of curl and Git, as they now support both
filenames on Windows.  Specifically, this support was added in commit
curl/curl@f9c7ba9, which was included
in curl v7.66.0.

To validate these changes, we also update our t/t-credentials.sh test
script so it runs the key "credentials from netrc" test twice on Windows,
once with a ".netrc" file and once with a legacy "_netrc" file.

As well, we adjust the other tests which previously used a "_netrc"
file on Windows to simply use a ".netrc" file, as this should work
on all systems now.

Author: chrisd8088

t/t-credentials.sh

@@ -437,61 +437,60 @@ state[]=lfstest:state2"
 )
 end_test
 
-
-if [[ $(uname) == *"MINGW"* ]]; then
-  NETRCFILE="$HOME/_netrc"
-else
-  NETRCFILE="$HOME/.netrc"
+NETRCFILES=".netrc"
+if [ "$IS_WINDOWS" -eq 1 ]; then
+  NETRCFILES+=" _netrc"
 fi
 
+for netrcfile in $NETRCFILES; do
+  begin_test "credentials from netrc ($netrcfile)"
+  (
+    set -e
 
-begin_test "credentials from netrc"
-(
-  set -e
+    printf "machine localhost\nlogin netrcuser\npassword netrcpass\n" >"$HOME/$netrcfile"
+    echo $HOME
+    echo "GITSERVER $GITSERVER"
+    cat "$HOME/$netrcfile"
 
-  printf "machine localhost\nlogin netrcuser\npassword netrcpass\n" >> "$NETRCFILE"
-  echo $HOME
-  echo "GITSERVER $GITSERVER"
-  cat $NETRCFILE
+    # prevent prompts on Windows particularly
+    export SSH_ASKPASS=
 
-  # prevent prompts on Windows particularly
-  export SSH_ASKPASS=
+    reponame="netrctest-$netrcfile"
+    setup_remote_repo "$reponame"
 
-  reponame="netrctest"
-  setup_remote_repo "$reponame"
+    clone_repo "$reponame" "${reponame}-assert"
 
-  clone_repo "$reponame" repo
+    # Need a remote named "localhost" or 127.0.0.1 in netrc will interfere with the other auth
+    git remote add "netrc" "$(echo $GITSERVER | sed s/127.0.0.1/localhost/)/netrctest"
+    git lfs env
 
-  # Need a remote named "localhost" or 127.0.0.1 in netrc will interfere with the other auth
-  git remote add "netrc" "$(echo $GITSERVER | sed s/127.0.0.1/localhost/)/netrctest"
-  git lfs env
+    git lfs track "*.dat"
+    echo "push a" > a.dat
+    git add .gitattributes a.dat
+    git commit -m "add a.dat"
 
-  git lfs track "*.dat"
-  echo "push a" > a.dat
-  git add .gitattributes a.dat
-  git commit -m "add a.dat"
+    GIT_TRACE=1 git lfs push netrc main 2>&1 | tee push.log
+    grep "Uploading LFS objects: 100% (1/1), 7 B" push.log
+    echo "any netrc credential calls:"
+    [ "4" -eq "$(cat push.log | grep "netrc: git credential" | wc -l)" ]
 
-  GIT_TRACE=1 git lfs push netrc main 2>&1 | tee push.log
-  grep "Uploading LFS objects: 100% (1/1), 7 B" push.log
-  echo "any netrc credential calls:"
-  [ "4" -eq "$(cat push.log | grep "netrc: git credential" | wc -l)" ]
+    echo "any netrc credential fills:"
+    [ "2" -eq "$(cat push.log | grep "netrc: git credential fill" | wc -l)" ]
 
-  echo "any netrc credential fills:"
-  [ "2" -eq "$(cat push.log | grep "netrc: git credential fill" | wc -l)" ]
-
-  echo "any netrc credential approvals:"
-  [ "2" -eq "$(cat push.log | grep "netrc: git credential approve" | wc -l)" ]
-)
-end_test
+    echo "any netrc credential approvals:"
+    [ "2" -eq "$(cat push.log | grep "netrc: git credential approve" | wc -l)" ]
+  )
+  end_test
+done
 
 begin_test "credentials from netrc with unknown keyword"
 (
   set -e
 
-  printf "machine localhost\nlogin netrcuser\nnot-a-key something\npassword netrcpass\n" >> "$NETRCFILE"
+  printf "machine localhost\nlogin netrcuser\nnot-a-key something\npassword netrcpass\n" >"$HOME/.netrc"
   echo $HOME
   echo "GITSERVER $GITSERVER"
-  cat $NETRCFILE
+  cat "$HOME/.netrc"
 
   # prevent prompts on Windows particularly
   export SSH_ASKPASS=
@@ -527,10 +526,10 @@ begin_test "credentials from netrc with bad password"
 (
   set -e
 
-  printf "machine localhost\nlogin netrcuser\npassword badpass\n" >> "$NETRCFILE"
+  printf "machine localhost\nlogin netrcuser\npassword badpass\n" >"$HOME/.netrc"
   echo $HOME
   echo "GITSERVER $GITSERVER"
-  cat $NETRCFILE
+  cat "$HOME/.netrc"
 
   # prevent prompts on Windows particularly
   export SSH_ASKPASS=
@@ -558,10 +557,10 @@ begin_test "credentials with bad netrc creds will retry"
 (
   set -e
 
-  printf "machine localhost\nlogin netrcuser\npassword badpassretry\n" >> "$NETRCFILE"
+  printf "machine localhost\nlogin netrcuser\npassword badpassretry\n" >"$HOME/.netrc"
   echo $HOME
   echo "GITSERVER $GITSERVER"
-  cat $NETRCFILE
+  cat "$HOME/.netrc"
 
   # prevent prompts on Windows particularly
   export SSH_ASKPASS=