hgweb: extract changelist entry generation into own function

I want to supplement changelist entries (used by shortlog and changelog
endpoints) with custom metadata from an extension. i.e. I have extra
per-changeset metadata that I wish to make available to templates so it
can be rendered on hgweb.

To facilitate this, I've extracted the logic for creating a changeset
data structure into its own function, where it can be wrapped by
extensions.

Ideally, hgweb would use the same templater as the command line and have
full access to templatekw.keywords. But that's a lot of work. This patch
gets us some of the benefit without all the work.

Many other hgweb commands could benefit from similar refactorings. I'm
going to wait to see how this patch is received before I go crazy on
extracting inline functions.

mercurial/hgweb/webcommands.py

@@ -282,31 +282,14 b' def changelog(web, req, tmpl, shortlog=F'
         if pos != -1:
             revs = web.repo.changelog.revs(pos, 0)
         curcount = 0
-        for i in revs:
-            ctx = web.repo[i]
-            n = ctx.node()
-            showtags = webutil.showtag(web.repo, tmpl, 'changelogtag', n)
-            files = webutil.listfilediffs(tmpl, ctx.files(), n, web.maxfiles)
-
+        for rev in revs:
             curcount += 1
             if curcount > revcount + 1:
                 break
-            yield {"parity": parity.next(),
-                   "author": ctx.user(),
-                   "parent": webutil.parents(ctx, i - 1),
-                   "child": webutil.children(ctx, i + 1),
-                   "changelogtag": showtags,
-                   "desc": ctx.description(),
-                   "extra": ctx.extra(),
-                   "date": ctx.date(),
-                   "files": files,
-                   "rev": i,
-                   "node": hex(n),
-                   "tags": webutil.nodetagsdict(web.repo, n),
-                   "bookmarks": webutil.nodebookmarksdict(web.repo, n),
-                   "inbranch": webutil.nodeinbranch(web.repo, ctx),
-                   "branches": webutil.nodebranchdict(web.repo, ctx)
-            }
+
+            entry = webutil.changelistentry(web, web.repo[rev], tmpl)
+            entry['parity'] = parity.next()
+            yield entry
 
     revcount = shortlog and web.maxshortchanges or web.maxchanges
     if 'revcount' in req.form:

mercurial/hgweb/webutil.py

@@ -249,6 +249,35 b' def filectx(repo, req):'
 
     return fctx
 
+def changelistentry(web, ctx, tmpl):
+    '''Obtain a dictionary to be used for entries in a changelist.
+
+    This function is called when producing items for the "entries" list passed
+    to the "shortlog" and "changelog" templates.
+    '''
+    repo = web.repo
+    rev = ctx.rev()
+    n = ctx.node()
+    showtags = showtag(repo, tmpl, 'changelogtag', n)
+    files = listfilediffs(tmpl, ctx.files(), n, web.maxfiles)
+
+    return {
+        "author": ctx.user(),
+        "parent": parents(ctx, rev - 1),
+        "child": children(ctx, rev + 1),
+        "changelogtag": showtags,
+        "desc": ctx.description(),
+        "extra": ctx.extra(),
+        "date": ctx.date(),
+        "files": files,
+        "rev": rev,
+        "node": hex(n),
+        "tags": nodetagsdict(repo, n),
+        "bookmarks": nodebookmarksdict(repo, n),
+        "inbranch": nodeinbranch(repo, ctx),
+        "branches": nodebranchdict(repo, ctx)
+    }
+
 def listfilediffs(tmpl, files, node, max):
     for f in files[:max]:
         yield tmpl('filedifflink', node=hex(node), file=f)