# HG changeset patch
# User Matt Harbison <matt_harbison@yahoo.com>
# Date 1510807395 18000
# Node ID e0a1b9ee93cdfb40ba43e8838a1edf4ea3ea24f3
# Parent  6864c405f0235d5c42937658049f0405d5d1abdc
lfs: add a repo requirement for this extension once an lfs file is committed

Largefiles does the same thing (also delayed until the first largefile commit),
to prevent access to the repo without the extension.  In the case of this
extension, not having the extension loaded while accessing an lfs file results
in cryptic errors about "missing processor for flag '0x2000'".  If enabled
locally but not remotely, the cryptic error message is about no common
changegroup version.  (It wants '03', which is currently experimental.)

The largefiles extension looks for any tracked file that starts with '.hglf/'.
Unfortunately, that doesn't work here.  I didn't see any way to get the files
that were just committed, without doing a full status.  But since there's no
secondary check on adding an lfs file once the extension is loaded and a
threshold set, the best practice is to only enable this locally on a repo that
needs it.  That should minimize the unnecessary overhead for repos without an
lfs file.

diff -r 6864c405f023 -r e0a1b9ee93cd hgext/lfs/__init__.py
--- a/hgext/lfs/__init__.py	Thu Nov 30 22:32:13 2017 +0900
+++ b/hgext/lfs/__init__.py	Wed Nov 15 23:43:15 2017 -0500
@@ -37,6 +37,7 @@
     exchange,
     extensions,
     filelog,
+    localrepo,
     registrar,
     revlog,
     scmutil,
@@ -84,6 +85,13 @@
 
 templatekeyword = registrar.templatekeyword()
 
+def featuresetup(ui, supported):
+    # don't die on seeing a repo with the lfs requirement
+    supported |= {'lfs'}
+
+def uisetup(ui):
+    localrepo.localrepository.featuresetupfuncs.add(featuresetup)
+
 def reposetup(ui, repo):
     # Nothing to do with a remote repo
     if not repo.local():
@@ -98,6 +106,17 @@
     # Push hook
     repo.prepushoutgoinghooks.add('lfs', wrapper.prepush)
 
+    if 'lfs' not in repo.requirements:
+        def checkrequireslfs(ui, repo, **kwargs):
+            if 'lfs' not in repo.requirements:
+                ctx = repo[kwargs['node']]
+                # TODO: is there a way to just walk the files in the commit?
+                if any(ctx[f].islfs() for f in ctx.files()):
+                    repo.requirements.add('lfs')
+                    repo._writerequirements()
+
+        ui.setconfig('hooks', 'commit.lfs', checkrequireslfs, 'lfs')
+
 def wrapfilelog(filelog):
     wrapfunction = extensions.wrapfunction
 
diff -r 6864c405f023 -r e0a1b9ee93cd tests/test-lfs.t
--- a/tests/test-lfs.t	Thu Nov 30 22:32:13 2017 +0900
+++ b/tests/test-lfs.t	Wed Nov 15 23:43:15 2017 -0500
@@ -20,7 +20,11 @@
 
 # Commit large file
   $ echo $LONG > largefile
+  $ grep lfs .hg/requires
+  [1]
   $ hg commit --traceback -Aqm "add large file"
+  $ grep lfs .hg/requires
+  lfs
 
 # Ensure metadata is stored
   $ hg debugdata largefile 0