refactor(server): Replace log calls with logrus

This introduces a structured logging library that can be used (next
step) to attach additional metadata to log entries.

tools/nixery/server/builder/archive.go

@@ -10,11 +10,11 @@ package builder
 import (
 	"archive/tar"
 	"io"
-	"log"
 	"os"
 	"path/filepath"
 
 	"github.com/google/nixery/layers"
+	log "github.com/sirupsen/logrus"
 )
 
 // Create a new tarball from each of the paths in the list and write the tarball

tools/nixery/server/builder/builder.go

@@ -26,7 +26,6 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
-	"log"
 	"net/http"
 	"net/url"
 	"os"
@@ -38,6 +37,7 @@ import (
 	"github.com/google/nixery/config"
 	"github.com/google/nixery/layers"
 	"github.com/google/nixery/manifest"
+	log "github.com/sirupsen/logrus"
 	"golang.org/x/oauth2/google"
 )
 

tools/nixery/server/builder/cache.go

@@ -19,11 +19,11 @@ import (
 	"encoding/json"
 	"io"
 	"io/ioutil"
-	"log"
 	"os"
 	"sync"
 
 	"github.com/google/nixery/manifest"
+	log "github.com/sirupsen/logrus"
 )
 
 // LocalCache implements the structure used for local caching of

tools/nixery/server/config/config.go

@@ -19,10 +19,10 @@ package config
 
 import (
 	"io/ioutil"
-	"log"
 	"os"
 
 	"cloud.google.com/go/storage"
+	log "github.com/sirupsen/logrus"
 )
 
 // Load (optional) GCS bucket signing data from the GCS_SIGNING_KEY and

tools/nixery/server/config/pkgsource.go

@@ -17,10 +17,11 @@ import (
 	"crypto/sha1"
 	"encoding/json"
 	"fmt"
-	"log"
 	"os"
 	"regexp"
 	"strings"
+
+	log "github.com/sirupsen/logrus"
 )
 
 // PkgSource represents the source from which the Nix package set used

tools/nixery/server/go-deps.nix

@@ -117,4 +117,13 @@
       sha256 = "1b7q6haabnp53igpmvr6a2414yralhbrldixx4kbxxg1apy8jdjg";
     };
   }
+  {
+    goPackagePath = "github.com/sirupsen/logrus";
+    fetch = {
+      type = "git";
+      url = "https://github.com/sirupsen/logrus";
+      rev = "de736cf91b921d56253b4010270681d33fdf7cb5";
+      sha256 = "1qixss8m5xy7pzbf0qz2k3shjw0asklm9sj6zyczp7mryrari0aj";
+    };
+  }
 ]

tools/nixery/server/layers/grouping.go

@@ -105,11 +105,11 @@ package layers
 import (
 	"crypto/sha1"
 	"fmt"
-	"log"
 	"regexp"
 	"sort"
 	"strings"
 
+	log "github.com/sirupsen/logrus"
 	"gonum.org/v1/gonum/graph/flow"
 	"gonum.org/v1/gonum/graph/simple"
 )

tools/nixery/server/main.go

@@ -30,7 +30,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
-	"log"
 	"net/http"
 	"regexp"
 	"time"
@@ -39,6 +38,7 @@ import (
 	"github.com/google/nixery/builder"
 	"github.com/google/nixery/config"
 	"github.com/google/nixery/layers"
+	log "github.com/sirupsen/logrus"
 )
 
 // ManifestMediaType is the Content-Type used for the manifest itself. This