CI validates WASM support

For now failure is allowed as no work was done, but this should confirm the crate can at least be compiled
to that target.

We try different targets, including WASI, for good measure, and already build crates that are naturally working.

Author: Byron

.github/workflows/wasm.yml

@@ -0,0 +1,35 @@
+name: WASM
+
+on:
+  push:
+    branches: [ main ]
+    tags-ignore: [ '*' ]
+    paths:
+      - '.github/**'
+      - 'git-pack/**'
+      - '*.toml'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '.github/**'
+      - 'git-pack/**'
+      - '*.toml'
+
+jobs:
+  wasm:
+    name: WebAssembly
+    runs-on: ubuntu-latest
+    continue-on-error: true
+    strategy:
+      matrix:
+        target: [ wasm32-unknown-unknown, wasm32-wasi ]
+    steps:
+      - uses: actions/checkout@master
+      - name: Install Rust
+        run: rustup update stable && rustup default stable && rustup target add ${{ matrix.target }}
+      - uses: Swatinem/rust-cache@v2
+      - run: set +x; for name in git-actor git-attributes git-bitmap git-chunk git-command git-commitgraph git-date git-glob git-hash git-hashtable git-mailmap git-object git-packetline git-path git-pathspec git-quote git-refspec git-revision git-traverse git-validate; do (cd $name && cargo build --target ${{ matrix.target }}); done
+        name: crates without feature toggles
+      - run: set +x; for feature in progress fs-walkdir-parallel parallel io-pipe crc32 zlib zlib-rust-backend fast-sha1 rustsha1 cache-efficiency-debug; do (cd git-features && cargo build --features $feature --target ${{ matrix.target }}); done
+        name: features of git-features
+#      - run: cargo build -p git-pack --target ${{ matrix.target }} // TODO: make something like it work

git-path/src/convert.rs

@@ -54,7 +54,7 @@ pub fn try_into_bstr<'a>(path: impl Into<Cow<'a, Path>>) -> Result<Cow<'a, BStr>
                 use std::os::wasi::ffi::OsStringExt;
                 path.into_os_string().into_vec().into()
             };
-            #[cfg(not(unix))]
+            #[cfg(not(any(unix, target_os = "wasi")))]
             let p: BString = path.into_os_string().into_string().map_err(|_| Utf8Error)?.into();
             p
         }),
@@ -69,7 +69,7 @@ pub fn try_into_bstr<'a>(path: impl Into<Cow<'a, Path>>) -> Result<Cow<'a, BStr>
                 use std::os::wasi::ffi::OsStrExt;
                 path.as_os_str().as_bytes().into()
             };
-            #[cfg(not(unix))]
+            #[cfg(not(any(unix, target_os = "wasi")))]
             let p: &BStr = path.to_str().ok_or(Utf8Error)?.as_bytes().into();
             p
         }),
@@ -94,11 +94,11 @@ pub fn try_from_byte_slice(input: &[u8]) -> Result<&Path, Utf8Error> {
         OsStr::from_bytes(input).as_ref()
     };
     #[cfg(target_os = "wasi")]
-    let p = {
+    let p: &Path = {
         use std::os::wasi::ffi::OsStrExt;
         OsStr::from_bytes(input).as_ref()
     };
-    #[cfg(not(unix))]
+    #[cfg(not(any(unix, target_os = "wasi")))]
     let p = Path::new(std::str::from_utf8(input).map_err(|_| Utf8Error)?);
     Ok(p)
 }
@@ -126,11 +126,11 @@ pub fn try_from_bstring(input: impl Into<BString>) -> Result<PathBuf, Utf8Error>
         std::ffi::OsString::from_vec(input.into()).into()
     };
     #[cfg(target_os = "wasi")]
-    let p = {
+    let p: PathBuf = {
         use std::os::wasi::ffi::OsStringExt;
         std::ffi::OsString::from_vec(input.into()).into()
     };
-    #[cfg(not(unix))]
+    #[cfg(not(any(unix, target_os = "wasi")))]
     let p = {
         use bstr::ByteVec;
         PathBuf::from(