commit: support .committemplate based on changed files

Summary:
See the test for an example. This can be useful to set templates for
sub-projects in a larger project.

Reviewed By: zzl0

Differential Revision: D49781544

fbshipit-source-id: ce9336c0b394377d3e90f135fcccf1fae01e81cb

eden/scm/lib/config/loader/src/builtin_static/core.rs

@@ -51,6 +51,9 @@ exportstack-max-bytes=1M
 
 log-implicit-follow-threshold=10000
 
+titles-namespace=true
+local-committemplate=true
+
 [zsh]
 completion-age=7
 completion-description=false
@@ -65,7 +68,4 @@ selectivepulldiscovery=true
 autopullhoistpattern=
 autopullpattern=re:^(?:default|remote)/[A-Za-z0-9._/-]+$
 hoist=default
-
-[experimental]
-titles-namespace=true
 "#);

eden/scm/sapling/cmdutil.py

@@ -4012,6 +4012,11 @@ def buildcommittemplate(repo, ctx, extramsg, ref):
         for k, v in repo.ui.configitems("committemplate")
     )
 
+    # load extra aliases based on changed files
+    if repo.ui.configbool("experimental", "local-committemplate"):
+        localtemplate = localcommittemplate(repo, ctx)
+        t.t.cache.update((k, templater.unquotestring(v)) for k, v in localtemplate)
+
     if not extramsg:
         extramsg = ""  # ensure that extramsg is string
 
@@ -4020,6 +4025,43 @@ def buildcommittemplate(repo, ctx, extramsg, ref):
     return pycompat.decodeutf8(ui.popbufferbytes(), errors="replace")
 
 
+def localcommittemplate(repo, ctx):
+    """return [(k, v)], local [committemplate] config based on changed files.
+
+    The local commit template only works for working copy ctx.
+
+    The local commit template is decided in these steps:
+    - First, calculate the common prefix of the changed files.
+      For example, the common prefix of a/x/1, a/x/2/3 is a/x.
+    - Then, find the config file, starting with prefix/.committemplate,
+      recursively look at parent directories until repo root.
+      For the above example, check a/x/.committemplate, then a/.committemplate,
+      then .committemplate from repo root.
+    - Load the config file. The format of the config file is ``key = value``,
+      similar to config files but without the [committemplate] header.
+    """
+
+    if ctx.node() is None:
+        files = ctx.files()
+        prefix = os.path.commonpath(files) if files else ""
+        wvfs = repo.wvfs
+        while True:
+            config_path = prefix + (prefix and "/" or "") + ".committemplate"
+            if wvfs.isdir(prefix) and wvfs.exists(config_path):
+                cfg = bindings.configloader.config()
+                content = wvfs.tryreadutf8(config_path)
+                cfg.parse(content, source=config_path)
+                section = ""
+                names = cfg.names(section)
+                return [(name, cfg.get(section, name)) for name in names]
+            next_prefix = os.path.dirname(prefix)
+            if next_prefix == prefix:
+                break
+            prefix = next_prefix
+
+    return []
+
+
 def hgprefix(msg):
     return "\n".join([f"{identity.tmplprefix()}: {a}" for a in msg.split("\n") if a])
 

eden/scm/tests/test-commit-localtemplate.t

@@ -0,0 +1,43 @@
+#debugruntest-compatible
+
+  $ newrepo
+  $ setconfig 'committemplate.changeset={foo}\n'
+  $ setconfig 'committemplate.foo=foo'
+
+Default commit template
+
+  $ HGEDITOR=cat hg commit --config ui.allowemptycommit=true
+  foo
+  abort: commit message unchanged
+  [255]
+
+  $ mkdir -p x/y/z/k z/y
+  $ touch x/y/z/k/1 x/y/z/1 x/y/1 x/1 z/y/1
+  $ echo 'foo = z' > x/y/z/.committemplate
+  $ echo 'foo = y' > x/y/.committemplate
+  $ echo 'foo = x' > x/.committemplate
+  $ echo 'foo = root' > .committemplate
+
+When x/y/z/k/.committemplate does not exist, check parents x/y/z:
+
+  $ hg add -q x/y/z/k/1
+  $ HGEDITOR=cat hg commit --config ui.allowemptycommit=true
+  z
+  abort: commit message unchanged
+  [255]
+
+Common prefix is now y:
+
+  $ hg add -q x/y/1
+  $ HGEDITOR=cat hg commit --config ui.allowemptycommit=true
+  y
+  abort: commit message unchanged
+  [255]
+
+Common prefix is now repo root:
+
+  $ hg add z/y/1
+  $ HGEDITOR=cat hg commit --config ui.allowemptycommit=true
+  root
+  abort: commit message unchanged
+  [255]