ci: use git-sdk-64-minimal

This is a (partial) backport of the improvements of the Azure Pipeline
made in Git for Windows v2.21.0.

The major benefit is that it makes the task to initialize the Git for
Windows SDK *a lot* faster.

It would also have worked around a problem where an MSYS2 update breaks
t6500.13, and it will work around similar problems in the future, as the
Azure Pipeline that updates git-sdk-64-minimal will not publish a new
artifact unless Git's test suite (as of upstream's current `master`)
passes.

Author: dscho

azure-pipelines.yml

@@ -175,53 +175,23 @@ phases:
     env:
       GITFILESHAREPWD: $(gitfileshare.pwd)
   - powershell: |
-       # Helper to check the error level of the latest command (exit with error when appropriate)
-       function c() { if (!$?) { exit(1) } }
-
-       # Add build agent's MinGit to PATH
-       $env:PATH = $env:AGENT_HOMEDIRECTORY +"\externals\\git\cmd;" +$env:PATH
-
-       # Helper to initialize (or update) a Git worktree
-       function init ($path, $url, $set_origin) {
-           if (Test-Path $path) {
-               cd $path; c
-               if (Test-Path .git) {
-                   git init; c
-               } else {
-                   git status
-               }
-           } else {
-               git init $path; c
-               cd $path; c
-           }
-           git config core.autocrlf false; c
-           git config core.untrackedCache true; c
-           if (($set_origin -ne 0) -and !(git config remote.origin.url)) {
-               git remote add origin $url; c
-           }
-           git fetch --depth=1 $url master; c
-           git reset --hard FETCH_HEAD; c
-           git clean -df; c
-       }
-
-       # Initialize Git for Windows' SDK
-       $sdk_path = "$(Build.SourcesDirectory)\git-sdk-64"
-       init "$sdk_path" "https://dev.azure.com/git-for-windows/git-sdk-64/_git/git-sdk-64" 0
-       init usr\src\build-extra https://github.com/git-for-windows/build-extra 1
-
-       # Let Git ignore the SDK and the test-cache
-       "/git-sdk-64/`n/test-cache/`n" | Out-File -NoNewLine -Encoding ascii -Append "$(Build.SourcesDirectory)\.git\info\exclude"
-
-       # Help MSYS2 runtime startup by initializing /etc/passwd
-       & "$sdk_path\git-cmd" --command=usr\\bin\\bash.exe -lc "mkpasswd -c >>/etc/passwd"; c
-    displayName: 'Initialize the Git for Windows SDK'
+      $urlbase = "https://dev.azure.com/git-for-windows/git/_apis/build/builds"
+      $id = ((Invoke-WebRequest -UseBasicParsing "${urlbase}?definitions=22&statusFilter=completed&resultFilter=succeeded&`$top=1").content | ConvertFrom-JSON).value[0].id
+      $downloadUrl = ((Invoke-WebRequest -UseBasicParsing "${urlbase}/$id/artifacts").content | ConvertFrom-JSON).value[1].resource.downloadUrl
+      (New-Object Net.WebClient).DownloadFile($downloadUrl,"git-sdk-64-minimal.zip")
+      Expand-Archive git-sdk-64-minimal.zip -DestinationPath "$(Build.SourcesDirectory)" -Force
+      Remove-Item git-sdk-64-minimal.zip
+
+      # Let Git ignore the SDK and the test-cache
+      "/git-sdk-64-minimal/`n/test-cache/`n" | Out-File -NoNewLine -Encoding ascii -Append "$(Build.SourcesDirectory)\.git\info\exclude"
+    displayName: 'Download git-sdk-64-minimal'
   - powershell: |
        # Helper to check the error level of the latest command (exit with error when appropriate)
        function c() { if (!$?) { exit(1) } }
 
        cd "$(Build.SourcesDirectory)"; c
 
-       git-sdk-64\git-cmd --command=usr\\bin\\bash.exe -lc @"
+       & git-sdk-64-minimal\usr\bin\bash.exe -lc @"
          export MAKEFLAGS=-j10
          export DEVELOPER=1
          export NO_PERL=1