Fixed self-assign warnings discovered by clang

Doing this now specifically because clang does not have
-Wjump-misses-init, but I've been looking for an excuse to remove these
for a while.

These warning flags create more annoyance than they add value. There is
probably a reason they aren't included in -Wall + -Wextra.

-Wshadow specifically is potentially harmful as it forces coming up with
new, sometimes less descriptive names for repeated variables.

Dependent projects should use different flags for their dependencies if
this introduces problems.

.github/workflows/test.yml

@@ -292,6 +292,27 @@ jobs:
       - name: test-valgrind
         run: make test TESTFLAGS+="-k --valgrind"
 
+  # test that compilation is warning free under clang
+  clang:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - name: install
+        run: |
+          # need toml, also pip3 isn't installed by default?
+          sudo apt-get update -qq
+          sudo apt-get install -qq python3 python3-pip
+          sudo pip3 install toml
+      - name: install-clang
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -qq clang
+          echo "CC=clang" >> $GITHUB_ENV
+          clang --version
+      # no reason to not test again
+      - name: test-clang
+        run: make test TESTFLAGS+="-k"
+
   # self-host with littlefs-fuse for a fuzz-like test
   fuse:
     runs-on: ubuntu-20.04

Makefile

@@ -41,8 +41,7 @@ override CFLAGS += -DLFS_YES_TRACE
 endif
 override CFLAGS += -g3
 override CFLAGS += -I.
-override CFLAGS += -std=c99 -Wall -pedantic
-override CFLAGS += -Wextra -Wshadow -Wjump-misses-init -Wundef
+override CFLAGS += -std=c99 -Wall -Wextra -pedantic
 
 ifdef VERBOSE
 override TESTFLAGS     += -v

lfs.c

@@ -865,11 +865,6 @@ static int lfs_dir_traverse(lfs_t *lfs,
                 };
                 sp += 1;
 
-                dir = dir;
-                off = off;
-                ptag = ptag;
-                attrs = attrs;
-                attrcount = attrcount;
                 tmask = 0;
                 ttag = 0;
                 begin = 0;