Move uncritical files into etc/ (#350)

This is mainly just to reduce the amount of files in the project root.
The criteria of what gets into `etc/` are the following:

* The file should not be necessary for building nsxiv. This excludes the
  `icon/*` stuff since that's needed by `window.c`.
* The file shouldn't have any valid reason to stay in the project root.
  This excludes things like `README.md`, `.gitignore` etc.

Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/350
Reviewed-by: explosion-mental <explosion-mental@noreply.codeberg.org>

etc/woodpecker/CFLAGS

@@ -0,0 +1,13 @@
+# vanilla flags
+-std=c99 -Wall -pedantic
+# optimizations: enables extra warnings and deeper analysis thus catches more errors/warnings
+-O3 -flto
+# treat warnings as errors
+-Werror
+# extra flags
+-Wextra -Wshadow -Wvla -Wpointer-arith
+-Wundef -Wstrict-overflow=4 -Wwrite-strings -Wunreachable-code
+-Wbad-function-cast -Wdeclaration-after-statement
+-Wmissing-prototypes -Wstrict-prototypes
+# silence
+-Wno-unused-parameter -Wno-missing-field-initializers

etc/woodpecker/analysis.yml

@@ -0,0 +1,28 @@
+branches: master
+
+pipeline:
+  analysis:
+    image: alpine
+    commands: |
+      apk add --no-cache build-base cppcheck clang-extra-tools \
+          imlib2-dev xorgproto \
+          libxft-dev libexif-dev giflib-dev libwebp-dev >/dev/null
+      make config.h version.h
+      std="c99"
+      run_cppcheck() {
+        cppcheck --std="$std" --enable=performance,portability \
+          --force --quiet --inline-suppr --error-exitcode=1 \
+          --max-ctu-depth=8 -j"$(nproc)" \
+          $(make OPT_DEP_DEFAULT="$1" dump_cppflags) \
+          --suppress=varFuncNullUB --suppress=uninitvar \
+          *.c
+      }
+      run_tidy() {
+        checks="$(sed '/^#/d' etc/woodpecker/clang-tidy-checks | paste -d ',' -s)"
+        clang-tidy --warnings-as-errors="*" --checks="$checks" --quiet *.c \
+                   -- -std="$std" $(make OPT_DEP_DEFAULT="$1" dump_cppflags)
+      }
+      run_cppcheck "0"
+      run_cppcheck "1"
+      run_tidy "0"
+      run_tidy "1"

etc/woodpecker/build.yml

@@ -0,0 +1,28 @@
+branches: master
+
+# NOTE: "stable" tcc is too old and fails at linking. instead fetching a recent known working commit.
+pipeline:
+  build:
+    image: alpine
+    environment:
+      - TCC_SHA=027b8fb9b88fe137447fb8bb1b61079be9702472
+    commands: |
+      apk add --no-cache \
+          imlib2 imlib2-dev xorgproto \
+          libxft libxft-dev libexif libexif-dev giflib giflib-dev libwebp libwebp-dev \
+          gcc clang llvm llvm-dev build-base wget ca-certificates >/dev/null
+      wget "https://github.com/TinyCC/tinycc/archive/$TCC_SHA.tar.gz" >/dev/null
+      tar xzf "$TCC_SHA.tar.gz" >/dev/null
+      ( cd "tinycc-$TCC_SHA" && ./configure --config-musl && make -s -j"$(nproc)" && make install; ) >/dev/null
+      CFLAGS="$(sed '/^#/d' etc/woodpecker/CFLAGS | paste -d ' ' -s)"
+      build () {
+        for cc in "gcc" "clang" "tcc"; do
+          echo "### $cc - $2 build ###"
+          make clean && make -s -j"$(nproc)" CC="$cc" CFLAGS="$CFLAGS" LDFLAGS="$CFLAGS" OPT_DEP_DEFAULT="$1"
+        done
+      }
+      # full-build #
+      build "1" "full"
+      # ensure minimal-build works without opt deps installed
+      apk del libxft libxft-dev libexif libexif-dev giflib giflib-dev libwebp libwebp-dev >/dev/null
+      build "0" "minimal"

etc/woodpecker/clang-tidy-checks

@@ -0,0 +1,17 @@
+# checks
+clang-analyzer-*,clang-diagnostic-*,bugprone-*,performance-*,modernize-*
+misc-*,readability-*,android-cloexec-*,cert-*
+llvm-include-order
+
+# silence
+-misc-unused-parameters
+-bugprone-easily-swappable-parameters,-bugprone-narrowing-conversions,-bugprone-incorrect-roundings
+-bugprone-implicit-widening-of-multiplication-result,-bugprone-integer-division
+-readability-braces-around-statements,-readability-magic-numbers,-readability-isolate-declaration
+-readability-function-cognitive-complexity,-readability-else-after-return
+-readability-uppercase-literal-suffix,-readability-avoid-const-params-in-decls
+-android-cloexec-fopen,-android-cloexec-pipe
+
+# false positive warnings
+-clang-analyzer-valist.Uninitialized
+-misc-no-recursion

etc/woodpecker/spell.yml

@@ -0,0 +1,9 @@
+branches: master
+
+# NOTE: codespell not available on stable alpine, use edge
+pipeline:
+  spell-check:
+    image: alpine:edge
+    commands: |
+      apk add --no-cache -X http://dl-cdn.alpinelinux.org/alpine/edge/testing py3-codespell git >/dev/null
+      git ls-files | sed '/\.png$/d' | xargs codespell