utils/changelog: Fixed --tag option, new --galaxy option

The --tag TAG option is now printing the changes for the given TAG and
not since the given tag. The new option --galaxy is printing the changelog
since the latest tag and also for the latest tag.

These changes are simplifying the generation of the changelog file that
is needed to pass the tests for galaxy and AutomationHub collections.

utils/changelog

@@ -25,48 +25,6 @@ import argparse
 import subprocess
 
 
-usage = "Usage: changelog [options] [<new version>]"
-parser = argparse.ArgumentParser(usage=usage)
-parser.add_argument("--tag", dest="tag",
-                    help="git tag")
-options, args = parser.parse_known_args()
-
-if len(args) == 1:
-    new_version = args[0]
-elif len(args) != 0:
-    parser.error("new version is not set")
-else:
-    new_version = None
-
-if options.tag is None:
-    tag = subprocess.check_output(
-        "git describe --tags $(git rev-list --tags --max-count=1)",
-        shell=True)
-    options.tag = tag.decode("utf-8").strip()
-
-version = options.tag[1:]
-
-command = ["git", "log", "%s.." % options.tag]
-process = subprocess.run(command,
-                         stdout=subprocess.PIPE,
-                         stderr=subprocess.PIPE)
-
-if process.returncode != 0:
-    print("git log failed: %s" % process.stderr.decode("utf8").split("\n")[0])
-    sys.exit(1)
-
-if new_version is not None:
-    s = "ansible-freeipa-%s" % new_version
-    print(s)
-    print("=" * len(s))
-    print()
-
-commits = {}
-prs = {}
-authors = {}
-
-lines = process.stdout.decode("utf-8").split("\n")
-
 class Ref:
     def __init__(self, commit):
         self.commit = commit
@@ -75,11 +33,11 @@ class Ref:
 def store(commits, prs, authors, commit, author, merge, msg):
     if commit is not None:
         if msg[0].startswith("Merge pull request #"):
-            pr = int(msg[0].split()[3][1:])
+            pr_ref = int(msg[0].split()[3][1:])
             if len(msg) > 1:
-                prs[pr] = msg[1].strip()
+                prs[pr_ref] = msg[1].strip()
             else:
-                prs[pr] = Ref(merge)
+                prs[pr_ref] = Ref(merge)
         else:
             commits[commit] = msg[0].strip()
             authors.setdefault(author, []).append(commit)
@@ -93,6 +51,45 @@ def get_commit(commits, commit):
     return commit
 
 
+def get_output(command):
+    try:
+        ret = subprocess.check_output(command, shell=True)
+        ret = ret.decode("utf-8").strip()
+    except subprocess.CalledProcessError:
+        print("Command '%s' failed" % command)
+        sys.exit(1)
+    return ret
+
+
+def changelog(tag):
+    prev_tag = None
+    if tag is not None and tag != "":
+        prev_tag = get_output(
+            "git describe --tag --abbrev=0 --always '%s^'" % tag)
+    else:
+        tag = get_output("git describe --tags --abbrev=0 "
+                         "$(git rev-list --tags --max-count=1)")
+
+    version = tag[1:]
+
+    if prev_tag is not None:
+        command = ["git", "log", "%s..%s" % (prev_tag, tag)]
+    else:
+        command = ["git", "log", "%s.." % tag]
+    process = subprocess.run(command,
+                             stdout=subprocess.PIPE,
+                             stderr=subprocess.PIPE)
+
+    if process.returncode != 0:
+        print("git log failed: %s" %
+              process.stderr.decode("utf8").split("\n")[0])
+        sys.exit(1)
+
+    lines = process.stdout.decode("utf-8").split("\n")
+
+    commits = {}
+    prs = {}
+    authors = {}
     commit = None
     author = None
     merge = None
@@ -121,23 +118,30 @@ for line in lines:
     if commit:
         store(commits, prs, authors, commit, author, merge, msg)
 
-s = "Changes since %s" % version
-print("%s" % s)
-print("-" * len(s))
+    if prev_tag is not None:
+        line = "Changes for %s since %s" % (version, prev_tag[1:])
+    else:
+        line = "Changes since %s" % version
+    print("%s" % line)
+    print("-" * len(line))
     print()
 
     prs_sorted = sorted(prs.keys(), reverse=True)
-for pr in prs_sorted:
-    if isinstance(prs[pr], Ref):
-        msg = get_commit(commits, prs[pr].commit)
+    for pr_ref in prs_sorted:
+        if isinstance(prs[pr_ref], Ref):
+            msg = get_commit(commits, prs[pr_ref].commit)
         else:
-        msg = prs[pr]
-    print("  - %s (#%d)" % (msg, pr))
+            msg = prs[pr_ref]
+        print("  - %s (#%d)" % (msg, pr_ref))
     print()
 
-s = "Detailed changelog since %s by author" % version
-print("%s" % s)
-print("-" * len(s))
+    if prev_tag is not None:
+        line = "Detailed changelog for %s since %s by author" % (version,
+                                                                 prev_tag[1:])
+    else:
+        line = "Detailed changelog since %s by author" % version
+    print("%s" % line)
+    print("-" * len(line))
     print("  %d authors, %d commits" % (len(authors), len(commits)))
     print()
 
@@ -147,3 +151,25 @@ for author in authors_sorted:
         for commit in authors[author]:
             print("  - %s" % commits[commit])
         print()
+
+
+parser = argparse.ArgumentParser(usage="Usage: changelog [options]")
+parser.add_argument("--tag", dest="tag", help="git tag")
+parser.add_argument("--galaxy", dest="galaxy", action="store_true",
+                    help="Create changelog for galaxy")
+options, args = parser.parse_known_args()
+
+if len(args) != 0:
+    parser.print_help()
+    sys.exit(1)
+
+if options.galaxy:
+    # Get latest tag
+    tag = get_output("git describe --tag --abbrev=0")
+    # get number of commits since latest tag
+    count = get_output("git rev-list '%s'.. --count" % tag)
+    if count != "0":
+        changelog(None)
+    changelog(tag)
+else:
+    changelog(options.tag)