Remove use of 'head' Unix tool in pcre2grep test (#743)

It's not available on Windows, but we hadn't noticed this because it's
provided by the Git for Windows tools which I have installed. This is
not good practice to require these tools as a build dependency.

I have replaced "head -1" with "pcre2grep -m1 .*" which matches and
prints the first line. For consistency, I have made the same change on
Unix.

Author: NWilson

.github/workflows/build.yml

@@ -129,13 +129,28 @@ jobs:
       matrix:
         arch: ["Win32", "x64"]
     steps:
+      - name: Setup
+        run: |
+          # GitHub Actions Windows images ship with Git for Windows, which is great,
+          # but it also pollutes the PATH with a lot of Unix tools which we don't
+          # want to require as build dependencies. This filters out the Unix tools.
+          # The GitHub images still include an absolute ton of junk in the PATH,
+          # but it seems to be rare for unintended dependencies to be added to our
+          # build scripts, so we can live with it for now.
+          $PATCHED_PATH = ($env:PATH -split ';' | Where-Object { $_ -notmatch 'C:\\Program Files\\Git\\usr\\bin|C:\\Program Files\\Git\\mingw64\\bin' }) -join ';'
+          # We can't seem to use $GITHUB_PATH here because that only allows
+          # appending to the PATH, not replacing it.
+          echo "PATH=$PATCHED_PATH" >> "$env:GITHUB_ENV"
+
       - name: Checkout
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           submodules: true
 
       - name: Configure
-        run: cmake -DPCRE2_SUPPORT_JIT=ON -DPCRE2_BUILD_PCRE2_16=ON -DPCRE2_BUILD_PCRE2_32=ON -DBUILD_SHARED_LIBS=ON -DBUILD_STATIC_LIBS=ON -DCMAKE_C_FLAGS="$CFLAGS_MSVC" -DCMAKE_COMPILE_WARNING_AS_ERROR=ON -B build -A ${{ matrix.arch }}
+        run: |
+          echo "PATH=$env:PATH"
+          cmake -DPCRE2_SUPPORT_JIT=ON -DPCRE2_BUILD_PCRE2_16=ON -DPCRE2_BUILD_PCRE2_32=ON -DBUILD_SHARED_LIBS=ON -DBUILD_STATIC_LIBS=ON -DCMAKE_C_FLAGS="$CFLAGS_MSVC" -DCMAKE_COMPILE_WARNING_AS_ERROR=ON -B build -A ${{ matrix.arch }}
 
       - name: Build
         run: cmake --build build --config Release

RunGrepTest

@@ -728,7 +728,7 @@ echo "---------------------------- Test 131 -----------------------------" >>tes
 echo "RC=$?" >>testtrygrep
 
 echo "---------------------------- Test 132 -----------------------------" >>testtrygrep
-(cd $srcdir; exec 3<testdata/grepinput; $valgrind $vjs $pcre2grep -m1 -A3 '^match' <&3; echo '---'; head -1 <&3; exec 3<&-) >>testtrygrep 2>&1
+(cd $srcdir; exec 3<testdata/grepinput; $valgrind $vjs $pcre2grep -m1 -A3 '^match' <&3; echo '---'; $valgrind $vjs $pcre2grep -m1 '.*' <&3; exec 3<&-) >>testtrygrep 2>&1
 echo "RC=$?" >>testtrygrep
 
 echo "---------------------------- Test 133 -----------------------------" >>testtrygrep

RunGrepTest.bat

@@ -693,7 +693,7 @@ echo RC=^%ERRORLEVEL%>>testtrygrep
 echo ---------------------------- Test 132 ----------------------------->>testtrygrep
 :: The Unix tests use fd3 here, but Windows only has StdIn/StdOut/StdErr (which, at the kernel
 :: level, are not even numbered). Use a subshell instead.
-(pushd %srcdir% & (%pcre2grep% -m1 -A3 "^match" & echo ---& head -1) <testdata/grepinput & popd) >>testtrygrep 2>&1
+(pushd %srcdir% & (%pcre2grep% -m1 -A3 "^match" & echo ---& %pcre2grep% -m1 ".*") <testdata/grepinput & popd) >>testtrygrep 2>&1
 echo RC=^%ERRORLEVEL%>>testtrygrep
 
 echo ---------------------------- Test 133 ----------------------------->>testtrygrep