debian packaging fixes (#301)

* remove leading article from description

resolves description-synopsis-starts-with-article
https://lintian.debian.org/tags/description-synopsis-starts-with-article.html

* ensure copyright is mode 644

resolves non-standard-file-perm
https://lintian.debian.org/tags/non-standard-file-perm.html

* add Depends line

Use dpkg-shlibdeps to work out shared library dependencies
and include them in a "Depends:" line

resolves missing-depends-line
https://lintian.debian.org/tags/missing-depends-line.html

* remove duplicate LICENSE file

resolves extra-license-file
https://lintian.debian.org/tags/extra-license-file.html

* change docs dir name to match package name

i.e: docs go in
/usr/share/doc/git-delta
/usr/share/doc/git-delta-musl
etc

not /usr/share/doc/delta

* include years in copyright notice

This brings the copyright notice into line with the expected format
resolves copyright-without-copyright-notice
https://lintian.debian.org/tags/copyright-without-copyright-notice.html

* provide a multi-line description

resolves extended-description-is-empty
https://lintian.debian.org/tags/extended-description-is-empty.html

Author: chris48s

etc/ci/before_deploy.sh

@@ -61,23 +61,28 @@ make_deb() {
 
     homepage="https://github.com/dandavison/delta"
     maintainer="Dan Davison <dandavison7@gmail.com>"
+    copyright_years="2019 - "$(date "+%Y")
 
     case $TARGET in
         x86_64*)
             architecture=amd64
             gcc_prefix=""
+            library_dir=""
             ;;
         i686*)
             architecture=i386
             gcc_prefix=""
+            library_dir=""
             ;;
         aarch64*)
             architecture=arm64
             gcc_prefix="aarch64-linux-gnu-"
+            library_dir="-l/usr/aarch64-linux-gnu/lib"
             ;;
         arm*hf)
             architecture=armhf
             gcc_prefix="arm-linux-gnueabihf-"
+            library_dir="-l/usr/arm-linux-gnueabihf/lib"
             ;;
         *)
             echo "make_deb: skipping target '${TARGET}'" >&2
@@ -99,16 +104,22 @@ make_deb() {
     install -Dm755 "target/$TARGET/release/$PROJECT_NAME" "$tempdir/usr/bin/$PROJECT_NAME"
     "${gcc_prefix}"strip "$tempdir/usr/bin/$PROJECT_NAME"
 
+    # Work out shared library dependencies
+    # dpkg-shlibdeps requires debian/control file. Dummy it and clean up
+    mkdir "./debian"
+    touch "./debian/control"
+    depends="$(dpkg-shlibdeps $library_dir -O "$tempdir/usr/bin/$PROJECT_NAME" 2> /dev/null | sed 's/^shlibs:Depends=//')"
+    rm -rf "./debian"
+
     # readme and license
-    install -Dm644 README.md "$tempdir/usr/share/doc/$PROJECT_NAME/README.md"
-    install -Dm644 LICENSE "$tempdir/usr/share/doc/$PROJECT_NAME/LICENSE"
-    cat > "$tempdir/usr/share/doc/$PROJECT_NAME/copyright" <<EOF
+    install -Dm644 README.md "$tempdir/usr/share/doc/$dpkgname/README.md"
+    cat > "$tempdir/usr/share/doc/$dpkgname/copyright" <<EOF
 Format: http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
 Upstream-Name: $PROJECT_NAME
 Source: $homepage
 
 Files: *
-Copyright: $maintainer
+Copyright: $copyright_years $maintainer
 License: MIT
 
 License: MIT
@@ -136,6 +147,7 @@ License: MIT
  IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  DEALINGS IN THE SOFTWARE.
 EOF
+    chmod 644 "$tempdir/usr/share/doc/$dpkgname/copyright"
 
     # Control file
     mkdir "$tempdir/DEBIAN"
@@ -146,9 +158,12 @@ Section: utils
 Priority: optional
 Maintainer: Dan Davison <dandavison7@gmail.com>
 Architecture: $architecture
+Depends: $depends
 Provides: $PROJECT_NAME
 Conflicts: $conflictname
-Description: A syntax highlighter for git.
+Description: Syntax highlighter for git.
+ Delta provides language syntax-highlighting, within-line insertion/deletion
+ detection, and restructured diff output for git on the command line.
 EOF
 
     fakeroot dpkg-deb --build "$tempdir" "${dpkgname}_${version}_${architecture}.deb"