tpl/tplimpl: Rework template management to get rid of concurrency issues

This more or less completes the simplification of the template handling code in Hugo started in v0.62.

The main motivation was to fix a long lasting issue about a crash in HTML content files  without front matter.

But this commit also comes with a big functional improvement.

As we now have moved the base template evaluation to the build stage we now use the same lookup rules for `baseof` as for `list` etc. type of templates.

This means that in this simple example you can have a `baseof` template for the `blog` section without having to duplicate the others:

```
layouts
├── _default
│   ├── baseof.html
│   ├── list.html
│   └── single.html
└── blog
    └── baseof.html
```

Also, when simplifying code, you often get rid of some double work, as shown in the "site building" benchmarks below.

These benchmarks looks suspiciously good, but I have repeated the below with ca. the same result. Compared to master:

```
name                              old time/op    new time/op    delta
SiteNew/Bundle_with_image-16        13.1ms ± 1%    10.5ms ± 1%  -19.34%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file-16    13.0ms ± 0%    10.7ms ± 1%  -18.05%  (p=0.029 n=4+4)
SiteNew/Tags_and_categories-16      46.4ms ± 2%    43.1ms ± 1%   -7.15%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs-16            52.2ms ± 2%    47.8ms ± 1%   -8.30%  (p=0.029 n=4+4)
SiteNew/Deep_content_tree-16        77.9ms ± 1%    70.9ms ± 1%   -9.01%  (p=0.029 n=4+4)
SiteNew/Many_HTML_templates-16      43.0ms ± 0%    37.2ms ± 1%  -13.54%  (p=0.029 n=4+4)
SiteNew/Page_collections-16         58.2ms ± 1%    52.4ms ± 1%   -9.95%  (p=0.029 n=4+4)

name                              old alloc/op   new alloc/op   delta
SiteNew/Bundle_with_image-16        3.81MB ± 0%    2.22MB ± 0%  -41.70%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file-16    3.60MB ± 0%    2.01MB ± 0%  -44.20%  (p=0.029 n=4+4)
SiteNew/Tags_and_categories-16      19.3MB ± 1%    14.1MB ± 0%  -26.91%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs-16            70.7MB ± 0%    69.0MB ± 0%   -2.40%  (p=0.029 n=4+4)
SiteNew/Deep_content_tree-16        37.1MB ± 0%    31.2MB ± 0%  -15.94%  (p=0.029 n=4+4)
SiteNew/Many_HTML_templates-16      17.6MB ± 0%    10.6MB ± 0%  -39.92%  (p=0.029 n=4+4)
SiteNew/Page_collections-16         25.9MB ± 0%    21.2MB ± 0%  -17.99%  (p=0.029 n=4+4)

name                              old allocs/op  new allocs/op  delta
SiteNew/Bundle_with_image-16         52.3k ± 0%     26.1k ± 0%  -50.18%  (p=0.029 n=4+4)
SiteNew/Bundle_with_JSON_file-16     52.3k ± 0%     26.1k ± 0%  -50.16%  (p=0.029 n=4+4)
SiteNew/Tags_and_categories-16        336k ± 1%      269k ± 0%  -19.90%  (p=0.029 n=4+4)
SiteNew/Canonify_URLs-16              422k ± 0%      395k ± 0%   -6.43%  (p=0.029 n=4+4)
SiteNew/Deep_content_tree-16          401k ± 0%      313k ± 0%  -21.79%  (p=0.029 n=4+4)
SiteNew/Many_HTML_templates-16        247k ± 0%      143k ± 0%  -42.17%  (p=0.029 n=4+4)
SiteNew/Page_collections-16           282k ± 0%      207k ± 0%  -26.55%  (p=0.029 n=4+4)
```

Fixes #6716
Fixes #6760
Fixes #6768
Fixes #6778

1 files changed, 0 insertions, 182 deletions

diff --git a/output/layout_base.go b/output/layout_base.go
deleted file mode 100644
index 772002e68..000000000
--- a/output/layout_base.go
+++ /dev/null
@@ -1,182 +0,0 @@
-// Copyright 2017-present The Hugo Authors. All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package output
-
-import (
-	"fmt"
-	"path/filepath"
-	"strings"
-
-	"github.com/gohugoio/hugo/helpers"
-)
-
-const (
-	baseFileBase = "baseof"
-)
-
-var (
-	goTemplateInnerMarkers = [][]byte{[]byte("{{define"), []byte("{{ define"), []byte("{{- define"), []byte("{{-define")}
-)
-
-// TemplateNames represents a template naming scheme.
-type TemplateNames struct {
-	// The name used as key in the template map. Note that this will be
-	// prefixed with "_text/" if it should be parsed with text/template.
-	Name string
-
-	OverlayFilename string
-	MasterFilename  string
-}
-
-// TemplateLookupDescriptor describes the template lookup configuration.
-type TemplateLookupDescriptor struct {
-	// The full path to the site root.
-	WorkingDir string
-
-	// The path to the template relative the the base.
-	//  I.e. shortcodes/youtube.html
-	RelPath string
-
-	// The template name prefix to look for.
-	Prefix string
-
-	// All the output formats in play. This is used to decide if text/template or
-	// html/template.
-	OutputFormats Formats
-
-	FileExists  func(filename string) (bool, error)
-	ContainsAny func(filename string, subslices [][]byte) (bool, error)
-}
-
-func isShorthCodeOrPartial(name string) bool {
-	return strings.HasPrefix(name, "shortcodes/") || strings.HasPrefix(name, "partials/")
-}
-
-// CreateTemplateNames returns a TemplateNames object for a given template.
-func CreateTemplateNames(d TemplateLookupDescriptor) (TemplateNames, error) {
-
-	name := filepath.ToSlash(d.RelPath)
-	name = strings.TrimPrefix(name, "/")
-
-	if d.Prefix != "" {
-		name = strings.Trim(d.Prefix, "/") + "/" + name
-	}
-
-	var (
-		id TemplateNames
-	)
-
-	// The filename will have a suffix with an optional type indicator.
-	// Examples:
-	// index.html
-	// index.amp.html
-	// index.json
-	filename := filepath.Base(d.RelPath)
-	isPlainText := false
-	outputFormat, found := d.OutputFormats.FromFilename(filename)
-
-	if found && outputFormat.IsPlainText {
-		isPlainText = true
-	}
-
-	var ext, outFormat string
-
-	parts := strings.Split(filename, ".")
-	if len(parts) > 2 {
-		outFormat = parts[1]
-		ext = parts[2]
-	} else if len(parts) > 1 {
-		ext = parts[1]
-	}
-
-	filenameNoSuffix := parts[0]
-
-	id.OverlayFilename = d.RelPath
-	id.Name = name
-
-	if isPlainText {
-		id.Name = "_text/" + id.Name
-	}
-
-	// Go templates may have both a base and inner template.
-	if isShorthCodeOrPartial(name) {
-		// No base template support
-		return id, nil
-	}
-
-	pathDir := filepath.Dir(d.RelPath)
-
-	innerMarkers := goTemplateInnerMarkers
-
-	var baseFilename string
-
-	if outFormat != "" {
-		baseFilename = fmt.Sprintf("%s.%s.%s", baseFileBase, outFormat, ext)
-	} else {
-		baseFilename = fmt.Sprintf("%s.%s", baseFileBase, ext)
-	}
-
-	// This may be a view that shouldn't have base template
-	// Have to look inside it to make sure
-	needsBase, err := d.ContainsAny(d.RelPath, innerMarkers)
-	if err != nil {
-		return id, err
-	}
-
-	if needsBase {
-		currBaseFilename := fmt.Sprintf("%s-%s", filenameNoSuffix, baseFilename)
-
-		// Look for base template in the follwing order:
-		//   1. <current-path>/<template-name>-baseof.<outputFormat>(optional).<suffix>, e.g. list-baseof.<outputFormat>(optional).<suffix>.
-		//   2. <current-path>/baseof.<outputFormat>(optional).<suffix>
-		//   3. _default/<template-name>-baseof.<outputFormat>(optional).<suffix>, e.g. list-baseof.<outputFormat>(optional).<suffix>.
-		//   4. _default/baseof.<outputFormat>(optional).<suffix>
-		//
-		// The filesystem it looks in a a composite of the project and potential theme(s).
-		pathsToCheck := createPathsToCheck(pathDir, baseFilename, currBaseFilename)
-
-		// We may have language code and/or "terms" in the template name. We want the most specific,
-		// but need to fall back to the baseof.html if needed.
-		// E.g. list-baseof.en.html and list-baseof.terms.en.html
-		// See #3893, #3856.
-		baseBaseFilename, currBaseBaseFilename := helpers.Filename(baseFilename), helpers.Filename(currBaseFilename)
-		p1, p2 := strings.Split(baseBaseFilename, "."), strings.Split(currBaseBaseFilename, ".")
-		if len(p1) > 0 && len(p1) == len(p2) {
-			for i := len(p1); i > 0; i-- {
-				v1, v2 := strings.Join(p1[:i], ".")+"."+ext, strings.Join(p2[:i], ".")+"."+ext
-				pathsToCheck = append(pathsToCheck, createPathsToCheck(pathDir, v1, v2)...)
-
-			}
-		}
-
-		for _, p := range pathsToCheck {
-			if ok, err := d.FileExists(p); err == nil && ok {
-				id.MasterFilename = p
-				break
-			}
-		}
-	}
-
-	return id, nil
-
-}
-
-func createPathsToCheck(baseTemplatedDir, baseFilename, currBaseFilename string) []string {
-	return []string{
-		filepath.Join(baseTemplatedDir, currBaseFilename),
-		filepath.Join(baseTemplatedDir, baseFilename),
-		filepath.Join("_default", currBaseFilename),
-		filepath.Join("_default", baseFilename),
-	}
-}