Add new option for detailed logging on dependency resolving

This adds command-line arg and config option, with option enabled
aptly is more verbose on internal depeendency resolving cycles:

```
Missing dependencies: file-rc (>= 0.8.16) [amd64], python:any (>= 2.7.1-0ubuntu2) [amd64], python3:any (>= 3.3.2-2~) [amd64], file-rc [amd64], perl (<< 5.17) [amd64], iptables-router (>= 1.2.3) [amd64], systemd [amd64], sgml-base (>= 1.26+nmu2) [amd64], sed (>= 4.1.2-8) [amd64]
Unsatisfied dependency: file-rc (>= 0.8.16) [amd64]
Unsatisfied dependency: python:any (>= 2.7.1-0ubuntu2) [amd64]
Unsatisfied dependency: python3:any (>= 3.3.2-2~) [amd64]
Unsatisfied dependency: file-rc [amd64]
Unsatisfied dependency: perl (<< 5.17) [amd64]
Unsatisfied dependency: iptables-router (>= 1.2.3) [amd64]
Unsatisfied dependency: systemd [amd64]
Injecting package: sgml-base_1.26+nmu4ubuntu1_all
Injecting package: sed_4.2.2-4ubuntu1_amd64
```

deb/list.go

@@ -3,6 +3,7 @@ package deb
 import (
 	"fmt"
 	"sort"
+	"strings"
 
 	"github.com/smira/aptly/aptly"
 	"github.com/smira/aptly/utils"
@@ -20,6 +21,8 @@ const (
 	DepFollowAllVariants
 	// DepFollowBuild pulls build dependencies
 	DepFollowBuild
+	// DepVerboseResolve emits additional logs while dependencies are being resolved
+	DepVerboseResolve
 )
 
 // PackageList is list of unique (by key) packages
@@ -346,6 +349,14 @@ func (l *PackageList) VerifyDependencies(options int, architectures []string, so
 		progress.ShutdownBar()
 	}
 
+	if options&DepVerboseResolve == DepVerboseResolve && progress != nil {
+		missingStr := make([]string, len(missing))
+		for i := range missing {
+			missingStr[i] = missing[i].String()
+		}
+		progress.ColoredPrintf("@{y}Missing dependencies:@| %s", strings.Join(missingStr, ", "))
+	}
+
 	return missing, nil
 }
 
@@ -462,6 +473,11 @@ func (l *PackageList) Search(dep Dependency, allMatches bool) (searchResults []*
 
 // Filter filters package index by specified queries (ORed together), possibly pulling dependencies
 func (l *PackageList) Filter(queries []PackageQuery, withDependencies bool, source *PackageList, dependencyOptions int, architecturesList []string) (*PackageList, error) {
+	return l.FilterWithProgress(queries, withDependencies, source, dependencyOptions, architecturesList, nil)
+}
+
+// FilterWithProgress filters package index by specified queries (ORed together), possibly pulling dependencies and displays progress
+func (l *PackageList) FilterWithProgress(queries []PackageQuery, withDependencies bool, source *PackageList, dependencyOptions int, architecturesList []string, progress aptly.Progress) (*PackageList, error) {
 	if !l.indexed {
 		panic("list not indexed, can't filter")
 	}
@@ -488,7 +504,7 @@ func (l *PackageList) Filter(queries []PackageQuery, withDependencies bool, sour
 			added = 0
 
 			// find missing dependencies
-			missing, err := result.VerifyDependencies(dependencyOptions, architecturesList, dependencySource, nil)
+			missing, err := result.VerifyDependencies(dependencyOptions, architecturesList, dependencySource, progress)
 			if err != nil {
 				return nil, err
 			}
@@ -501,9 +517,12 @@ func (l *PackageList) Filter(queries []PackageQuery, withDependencies bool, sour
 					continue
 				}
 
-				searchResults := l.Search(dep, false)
+				searchResults := l.Search(dep, true)
 				if searchResults != nil {
 					for _, p := range searchResults {
+						if dependencyOptions&DepVerboseResolve == DepVerboseResolve && progress != nil {
+							progress.ColoredPrintf("@{g}Injecting package@|: %s", p)
+						}
 						result.Add(p)
 						dependencySource.Add(p)
 						added++
@@ -511,6 +530,11 @@ func (l *PackageList) Filter(queries []PackageQuery, withDependencies bool, sour
 							break
 						}
 					}
+				} else {
+					if dependencyOptions&DepVerboseResolve == DepVerboseResolve && progress != nil {
+						progress.ColoredPrintf("@{r}Unsatisfied dependency@|: %s", dep.String())
+					}
+
 				}
 			}
 		}

deb/remote.go

@@ -491,14 +491,14 @@ func (repo *RemoteRepo) DownloadPackageIndexes(progress aptly.Progress, d aptly.
 }
 
 // ApplyFilter applies filtering to already built PackageList
-func (repo *RemoteRepo) ApplyFilter(dependencyOptions int, filterQuery PackageQuery) (oldLen, newLen int, err error) {
+func (repo *RemoteRepo) ApplyFilter(dependencyOptions int, filterQuery PackageQuery, progress aptly.Progress) (oldLen, newLen int, err error) {
 	repo.packageList.PrepareIndex()
 
 	emptyList := NewPackageList()
 	emptyList.PrepareIndex()
 
 	oldLen = repo.packageList.Len()
-	repo.packageList, err = repo.packageList.Filter([]PackageQuery{filterQuery}, repo.FilterWithDeps, emptyList, dependencyOptions, repo.Architectures)
+	repo.packageList, err = repo.packageList.FilterWithProgress([]PackageQuery{filterQuery}, repo.FilterWithDeps, emptyList, dependencyOptions, repo.Architectures, progress)
 	if repo.packageList != nil {
 		newLen = repo.packageList.Len()
 	}