user-manual: start revising "internals" chapter

diff --git a/git-am.sh b/git-am.sh
index 2c73d116b28d0d89d1fbdfc1d454506bff9e3f46..e69ecbfdb1a817b477aff8618f284a4c921e00e5 100755 (executable)
--- a/git-am.sh
+++ b/git-am.sh
@@ -290,6 +290,10 @@ do
                git-mailinfo $keep $utf8 "$dotest/msg" "$dotest/patch" \
                        <"$dotest/$msgnum" >"$dotest/info" ||
                        stop_here $this
+               test -s $dotest/patch || {
+                       echo "Patch is empty.  Was is split wrong?"
+                       stop_here $this
+               }
                git-stripspace < "$dotest/msg" > "$dotest/msg-clean"
                ;;
        esac
@@ -404,12 +408,10 @@ do
                # trust what the user has in the index file and the
                # working tree.
                resolved=
-               changed="$(git-diff-index --cached --name-only HEAD)"
-               if test '' = "$changed"
-               then
+               git-diff-index --quiet --cached HEAD && {
                        echo "No changes - did you forget to use 'git add'?"
                        stop_here_user_resolve $this
-               fi
+               }
                unmerged=$(git-ls-files -u)
                if test -n "$unmerged"
                then
@@ -431,13 +433,11 @@ do
                then
                    # Applying the patch to an earlier tree and merging the
                    # result may have produced the same tree as ours.
-                   changed="$(git-diff-index --cached --name-only HEAD)"
-                   if test '' = "$changed"
-                   then
-                           echo No changes -- Patch already applied.
-                           go_next
-                           continue
-                   fi
+                   git-diff-index --quiet --cached HEAD && {
+                       echo No changes -- Patch already applied.
+                       go_next
+                       continue
+                   }
                    # clear apply_status -- we have successfully merged.
                    apply_status=0
                fi