largefiles: set the extension as enabled locally after a clone requiring it

When cloning a repo that requires largefiles, the user had to either enable the
extension on the command line and then manually edit the local hgrc file after
the clone, or just enable it globally for the user.  Since it is a feature of
last resort, and materially affects even repos without any largefiles when it is
enabled, we should make it easier to not have it enabled globally.

This simply adds the enabling statement to the local hgrc if the requires file
mandates its use (which only happens after the first largefile is committed).
That means that a user who works with a mix of largefile and normal repos can
always clone with '--config extensions.largefiles=', and the extension is
permanently enabled or not as appropriate.

The change in test-largefiles.t is simply because the order of loading rebase
and largefiles changed.  The same change occurs if the order is flipped in the
hgrc file at the top of the test.

hgext/largefiles/overrides.py

@@ -821,6 +821,14 def hgclone(orig, ui, opts, *args, **kwa
         sourcerepo, destrepo = result
         repo = destrepo.local()
 
+        # If largefiles is required for this repo, permanently enable it locally
+        if 'largefiles' in repo.requirements:
+            fp = repo.vfs('hgrc', 'a', text=True)
+            try:
+                fp.write('\n[extensions]\nlargefiles=\n')
+            finally:
+                fp.close()
+
         # Caching is implicitly limited to 'rev' option, since the dest repo was
         # truncated at that point.  The user may expect a download count with
         # this option, so attempt whether or not this is a largefile repo.

tests/test-largefiles.t

@@ -1183,12 +1183,12 rebased or not.
   adding manifests
   adding file changes
   added 1 changesets with 2 changes to 2 files (+1 heads)
-  0 largefiles cached
   rebasing 8:f574fb32bb45 "modify normal file largefile in repo d"
   Invoking status precommit hook
   M sub/normal4
   M sub2/large6
   saved backup bundle to $TESTTMP/d/.hg/strip-backup/f574fb32bb45-dd1d9f80-backup.hg (glob)
+  0 largefiles cached
   $ [ -f .hg/largefiles/e166e74c7303192238d60af5a9c4ce9bef0b7928 ]
   $ hg log --template '{rev}:{node|short}  {desc|firstline}\n'
   9:598410d3eb9a  modify normal file largefile in repo d

tests/test-subrepo-deep-nested-change.t

@@ -46,12 +46,29 Cleaning both repositories, just as a cl
 
 Clone main
 
-  $ hg clone main cloned
+  $ hg --config extensions.largefiles= clone main cloned
   updating to branch default
   cloning subrepo sub1 from $TESTTMP/sub1
   cloning subrepo sub1/sub2 from $TESTTMP/sub2 (glob)
   3 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
+Largefiles is NOT enabled in the clone if the source repo doesn't require it
+  $ cat cloned/.hg/hgrc
+  # example repository config (see "hg help config" for more info)
+  [paths]
+  default = $TESTTMP/main (glob)
+  
+  # path aliases to other clones of this repo in URLs or filesystem paths
+  # (see "hg help config.paths" for more info)
+  #
+  # default-push = ssh://[e-mail]/hg/jdoes-fork
+  # my-fork      = ssh://[e-mail]/hg/jdoes-fork
+  # my-clone     = /home/jdoe/jdoes-clone
+  
+  [ui]
+  # name and email (local to this repository, optional), e.g.
+  # username = Jane Doe <[e-mail]>
+
 Checking cloned repo ids
 
   $ printf "cloned " ; hg id -R cloned
@@ -319,6 +336,31 Find an exact largefile match in a large
   ../archive_lf/sub1/sub2/large.bin
   $ rm -rf ../archive_lf
 
+The local repo enables largefiles if a largefiles repo is cloned
+  $ hg showconfig extensions
+  abort: repository requires features unknown to this Mercurial: largefiles!
+  (see http://mercurial.selenic.com/wiki/MissingRequirement for more information)
+  [255]
+  $ hg --config extensions.largefiles= clone -qU . ../lfclone
+  $ cat ../lfclone/.hg/hgrc
+  # example repository config (see "hg help config" for more info)
+  [paths]
+  default = $TESTTMP/cloned (glob)
+  
+  # path aliases to other clones of this repo in URLs or filesystem paths
+  # (see "hg help config.paths" for more info)
+  #
+  # default-push = ssh://[e-mail]/hg/jdoes-fork
+  # my-fork      = ssh://[e-mail]/hg/jdoes-fork
+  # my-clone     = /home/jdoe/jdoes-clone
+  
+  [ui]
+  # name and email (local to this repository, optional), e.g.
+  # username = Jane Doe <[e-mail]>
+  
+  [extensions]
+  largefiles=
+
 Find an exact match to a standin (should archive nothing)
   $ hg --config extensions.largefiles= archive -S -I 'sub/sub2/.hglf/large.bin' ../archive_lf
   $ find ../archive_lf 2> /dev/null | sort