Document path template functions

Fixes #452

content/en/functions/path.Base.md

@@ -0,0 +1,31 @@
+---
+title: path.Base
+description: Base returns the last element of a path.
+godocref:
+date: 2018-11-28
+publishdate: 2018-11-28
+lastmod: 2018-11-28
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [path, base]
+signature: ["path.Base PATH"]
+workson: []
+hugoversion: "0.40"
+relatedfuncs: [path.Dir, path.Ext, path.Split]
+deprecated: false
+---
+
+`path.Base` returns the last element of `PATH`.
+
+If `PATH` is empty, `.` is returned.
+
+**Note:** On Windows, `PATH` is converted to slash (`/`) separators.
+
+```
+{{ path.Base "a/news.html" }} → "news.html"
+{{ path.Base "news.html" }} → "news.html"
+{{ path.Base "a/b/c" }} → "c"
+{{ path.Base "/x/y/z/" }} → "z"
+```

content/en/functions/path.Dir.md

@@ -0,0 +1,32 @@
+---
+title: path.Dir
+description: Dir returns all but the last element of a path.
+godocref:
+date: 2018-11-28
+publishdate: 2018-11-28
+lastmod: 2018-11-28
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [path, dir]
+signature: ["path.Dir PATH"]
+workson: []
+hugoversion: "0.40"
+relatedfuncs: [path.Base, path.Ext, path.Split]
+deprecated: false
+---
+
+`path.Dir` returns all but the last element of `PATH`, typically `PATH`'s directory.
+
+The returned path will never end in a slash.
+If `PATH` is empty, `.` is returned.
+
+**Note:** On Windows, `PATH` is converted to slash (`/`) separators.
+
+```
+{{ path.Dir "a/news.html" }} → "a"
+{{ path.Dir "news.html" }} → "."
+{{ path.Dir "a/b/c" }} → "a/b"
+{{ path.Dir "/x/y/z" }} → "/x/y"
+```

content/en/functions/path.Ext.md

@@ -0,0 +1,29 @@
+---
+title: path.Ext
+description: Ext returns the file name extension of a path.
+godocref:
+date: 2018-11-28
+publishdate: 2018-11-28
+lastmod: 2018-11-28
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [path, ext, extension]
+signature: ["path.Ext PATH"]
+workson: []
+hugoversion: "0.40"
+relatedfuncs: [path.Base, path.Dir, path.Split]
+deprecated: false
+---
+
+`path.Ext` returns the file name extension `PATH`.
+
+The extension is the suffix beginning at the final dot in the final slash-separated element `PATH`;
+it is empty if there is no dot.
+
+**Note:** On Windows, `PATH` is converted to slash (`/`) separators.
+
+```
+{{ path.Ext "a/b/c/news.html" }} → ".html"
+```

content/en/functions/path.Join.md

@@ -0,0 +1,29 @@
+---
+title: path.Join
+description: Join path elements into a single path.
+godocref:
+date: 2018-11-28
+publishdate: 2018-11-28
+lastmod: 2018-11-28
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [path, join]
+signature: ["path.Join ELEMENT..."]
+workson: []
+hugoversion: "0.39"
+relatedfuncs: [path.Split]
+deprecated: false
+---
+
+`path.Join` joins path elements into a single path, adding a separating slash if necessary.
+All empty strings are ignored.
+
+**Note:** All path elements on Windows are converted to slash ('/') separators.
+
+```
+{{ path.Join "partial" "news.html" }} → "partial/news.html"
+{{ path.Join "partial/" "news.html" }} → "partial/news.html"
+{{ path.Join "foo/baz" "bar" }} → "foo/baz/bar"
+```

content/en/functions/path.Split.md

@@ -0,0 +1,31 @@
+---
+title: path.Split
+description: Split path immediately following the final slash.
+godocref:
+date: 2018-11-28
+publishdate: 2018-11-28
+lastmod: 2018-11-28
+categories: [functions]
+menu:
+  docs:
+    parent: "functions"
+keywords: [path, split]
+signature: ["path.Split PATH"]
+workson: []
+hugoversion: "0.39"
+relatedfuncs: [path.Split]
+deprecated: false
+---
+
+`path.Split` splits `PATH` immediately following the final slash, separating it into a directory and a base component.
+
+The returned values have the property that `PATH` = `DIR`+`BASE`.
+If there is no slash in `PATH`, it returns an empty directory and the base is set to `PATH`.
+
+**Note:** On Windows, `PATH` is converted to slash (`/`) separators.
+
+```
+{{ path.Split "a/news.html" }} → "a/", "news.html"
+{{ path.Split "news.html" }} → "", "news.html"
+{{ path.Split "a/b/c" }} → "a/b/", "c"
+```