New workflow to display incremental changes in manifests (#473)

* New diffing script between consecutive releases

* New workflow to get diffs

* Testing fixes

.github/workflows/diff-release.yml

@@ -0,0 +1,46 @@
+# Show differences between the submitted manifest and the previous
+# release of the same crate, to enable easier catching of problems
+
+name: Diff release
+
+on:
+  pull_request:
+    paths:
+      - 'index/**.toml'
+
+jobs:
+
+  diff:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Check out alire-index
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+        # Needed to be able to diff and obtain changed files. Furthermore, we
+        # need the full history or else grafted partial branches confuse the
+        # changed files detector
+
+#    - name: Set up GNAT toolchain (FSF)
+#      uses: ada-actions/toolchain@ce2020
+#      with:
+#        distrib: fsf # faster install?
+
+    - name: Set up stable `alr`
+      if: contains(github.base_ref, 'stable-')
+      uses: alire-project/setup-alire@v1
+      with:
+        toolchain: --disable-assistant # We don't need the compiler
+
+    - name: Set up devel `alr`
+      if: contains(github.base_ref, 'devel-')
+      uses: alire-project/setup-alire@v1
+      with:
+        toolchain: --disable-assistant # We don't need the compiler
+        branch: master
+
+    - name: Diff releases
+      run: scripts/diff-release.sh || true # No deal breaker if failed
+      shell: bash

scripts/diff-release.sh

@@ -0,0 +1,76 @@
+#!/bin/bash
+
+trap 'echo "ERROR at line ${LINENO} (code: $?)" >&2' ERR
+trap 'echo "Interrupted" >&2 ; exit 1' INT
+
+set -o errexit
+set -o nounset
+
+# Ensure all alr runs are non-interactive
+alias alr="alr -n"
+
+# Detect changes
+CHANGES=$(git diff --name-only HEAD~1)
+
+# Bulk changes for the record
+echo Changed files: $CHANGES
+
+# Disable assistant. This is necessary despite the setup-alire action doing it
+# too, because we sometimes run inside a Docker with fresh configuration
+alr toolchain --disable-assistant
+
+# Configure index
+alr index --del local >/dev/null || true # Simplifies local testing
+alr index --name local --add ./index
+
+# Remove community index in case it has been added before
+alr index --del community >/dev/null || true
+
+diff_opts=(--minimal -U0 --line-prefix "--| " --ignore-all-space --ignore-blank-lines --ignore-cr-at-eol)
+
+function diff_one() {
+    local file="$1"
+    local folder=$(dirname $file)
+    local crate=$(basename $file .toml | cut -f1 -d-)
+    local version=$(basename $file .toml | cut -f2- -d-)
+    local milestone="$crate=$version"
+
+    echo " "
+    echo "------8<------"
+
+    if echo $milestone | grep -q external; then
+        echo DIFFING external: $milestone
+        git diff "${diff_opts[@]}" HEAD~1 -- $file
+    else
+        echo DIFFING release: $milestone
+
+        # Locate the immediately precedent release
+
+        # For a first release, there's nothing to compare
+        if [ $(ls $folder | grep -v external | wc -l) -eq 1 ]; then
+            echo NOTHING to diff against, first crate release
+            return 0
+        fi
+
+        # Othewise, get from alr what's the immediately preceding version
+        local prev_milestone=$(alr show "$crate<$version" | head -1 | cut -f1 -d:)
+        echo DIFFING milestones $prev_milestone '-->' $milestone
+
+        if [ "$prev_milestone" == "ERROR" ]; then
+            echo ERROR extracting milestone:
+            alr show "$crate<$version"
+            return 1
+        fi
+
+        # Convert into filename
+        local prev_file=$folder/${prev_milestone//=/-}.toml
+
+        git diff --no-index "${diff_opts[@]}" -- $prev_file $file
+    fi
+
+    return 0
+}
+
+for file in $CHANGES; do
+    diff_one "$file" || true # keep on trying for different files
+done