add Transaction::partial_sign() (#4333)

* add partial sign

* nits

ci/nits.sh

@@ -30,7 +30,7 @@ declare print_free_tree=(
   'programs/stake_program/src'
 )
 
-if _ git grep -n --max-depth=0 "${prints[@]/#/-e }" -- "${print_free_tree[@]}"; then
+if _ git --no-pager grep -n --max-depth=0 "${prints[@]/#/-e }" -- "${print_free_tree[@]}"; then
     exit 1
 fi
 
@@ -39,14 +39,14 @@ fi
 # Default::default()
 #
 # Ref: https://github.com/solana-labs/solana/issues/2630
-if _ git grep -n 'Default::default()' -- '*.rs'; then
+if _ git --no-pager grep -n 'Default::default()' -- '*.rs'; then
     exit 1
 fi
 
 # Let's keep a .gitignore for every crate, ensure it's got
 #  /target/ in it
 declare gitignores_ok=true
-for i in $(git ls-files \*/Cargo.toml ); do
+for i in $(git --no-pager ls-files \*/Cargo.toml ); do
   dir=$(dirname "$i")
   if [[ ! -f $dir/.gitignore ]]; then
       echo 'error: nits.sh .gitnore missing for crate '"$dir" >&2