refactor!: remove go-git backend (#39487)

Removes the go-git backend so every build uses the git CLI backend. Its
Windows performance advantage is gone, it lacks SHA-256 support, and it
breaks repositories on Windows.

The performance changes moved to
https://github.com/go-gitea/gitea/pull/39526.

Fixes https://github.com/go-gitea/gitea/issues/38359
Fixes https://github.com/go-gitea/gitea/issues/34694

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

.github/workflows/cache-seeder.yml

@@ -37,22 +37,15 @@ jobs:
       - uses: ./.github/actions/go-setup
       - run: make deps-backend deps-tools
       - run: TAGS="bindata" make backend
-      - run: TAGS="bindata gogit" make backend
       - name: warm test compile cache (bindata)
         env:
           TAGS: bindata
           GOTEST_FLAGS: -race -list=^$$ -count=1
         run: make test-backend
-      - name: warm test compile cache (bindata gogit)
-        env:
-          TAGS: bindata gogit
-          GOTEST_FLAGS: -race -list=^$$ -count=1
-        run: make test-backend
       - name: warm integration compile cache
         run: |
           TAGS="bindata" make test-integration-compile
-          TAGS="bindata gogit" make test-integration-compile
-          TAGS="bindata gogit" GOTEST_FLAGS="-race" make test-integration-compile
+          TAGS="bindata" GOTEST_FLAGS="-race" make test-integration-compile
 
   lint:
     runs-on: ubuntu-latest

.github/workflows/pull-compliance.yml

@@ -93,13 +93,13 @@ jobs:
         env:
           GOOS: linux
           GOARCH: arm64
-          TAGS: bindata gogit
+          TAGS: bindata
       - name: build-backend-windows
         run: go build -ldflags '-s -w' -o gitea-windows
         env:
           GOOS: windows
           GOARCH: amd64
-          TAGS: bindata gogit
+          TAGS: bindata
       - name: build-backend-386
         run: go build -ldflags '-s -w' -o gitea-linux-386
         env:

.github/workflows/pull-db-tests.yml

@@ -95,17 +95,17 @@ jobs:
       - run: make deps-backend
       - run: make backend
         env:
-          TAGS: bindata gogit
+          TAGS: bindata
       - run: GITEA_TEST_DATABASE=sqlite make test-migration
         env:
-          TAGS: bindata gogit
+          TAGS: bindata
       - name: run tests
         run: GITEA_TEST_DATABASE=sqlite make test-integration
         timeout-minutes: 50
         env:
           # sqlite driver can contain large amount of Golang code, so don't use race detector for it, otherwise, extremely slow
           GOTEST_FLAGS: -timeout=40m
-          TAGS: bindata gogit
+          TAGS: bindata
 
   test-unit:
     if: needs.files-changed.outputs.backend == 'true'
@@ -163,13 +163,6 @@ jobs:
           GOTEST_FLAGS: -race -timeout=20m
           TAGS: bindata
           GITHUB_READ_TOKEN: ${{ secrets.GITHUB_READ_TOKEN }}
-      - name: unit-tests-gogit
-        run: make test-backend
-        env:
-          GOTEST_FLAGS: -race -timeout=20m
-          TAGS: bindata gogit
-          GITHUB_READ_TOKEN: ${{ secrets.GITHUB_READ_TOKEN }}
-          GITEA_TEST_CI_SKIP_EXTERNAL: true
       - run: make test-check
 
   test-mysql: