feat: Add prefix: 'string' option to linking when glob: true.

Allows one to store files in a directory or git-repo without the leading 
`.`, as in:

```
dotconf:
├── README.md
├── bin
│   ├── dotbot
│   ├── look
│   ├── pbfile
│   └── ...
├── dot
│   ├── bashrc
│   ├── gitconfig
│   ├── gitignore
│   ├── gorc
│   ├── login
│   ├── ...
│   ├── zshrc
│   └── zshenv
```

Can take a many-line dotbot.yml listing **each** file in `dotconf/dot`,
reducing it to five lines:

```
- link:
    ~/:
      path: dotconf/dot/*
      glob: true
      prefix: '.'
```

FIXES: #259

README.md

@@ -181,16 +181,22 @@ mapped to extended configuration dictionaries.
 | `force` | Force removes the old target, file or folder, and forces a new link (default: false) |
 | `relative` | Use a relative path to the source when creating the symlink (default: false, absolute links) |
 | `canonicalize` | Resolve any symbolic links encountered in the source to symlink to the canonical path (default: true, real paths) |
-| `glob` | Treat a `*` character as a wildcard, and perform link operations on all of those matches (default: false) |
 | `if` | Execute this in your `$SHELL` and only link if it is successful. |
 | `ignore-missing` | Do not fail if the source is missing and create the link anyway (default: false) |
-| `exclude` | Array of paths to remove from glob matches. Uses same syntax as `path`. Ignored if `glob` is `false`. (default: empty, keep all matches) |
+| `glob` | Treat `path` as a glob pattern, expanding patterns referenced below, linking all *files** matched. (default: false) |
+| `exclude` | Array of glob patterns to remove from glob matches. Uses same syntax as `path`. Ignored if `glob` is `false`. (default: empty, keep all matches) |
+| `prefix` | Prepend prefix prefix to basename of each file when linked, when `glob` is `true`. (default: '') |
 
-Dotbot uses [glob.glob](https://docs.python.org/3/library/glob.html#glob.glob)
-to resolve glob paths. However, due to its design, using a glob path such as
-`config/*` for example, will not match items that begin with `.`. To
-specifically capture items that begin with `.`, you will need to use a path
-like this: `config/.*`.
+When `glob: True`, Dotbot uses [glob.glob](https://docs.python.org/3/library/glob.html#glob.glob) to resolve glob paths, expanding Unix shell-style wildcards, which are **not** the same as regular expressions; Only the following are expanded:
+
+| Pattern  | Meaning                                                |
+|:---------|:-------------------------------------------------------|
+| `*`      | matches anything                                       |
+| `?`      | matches any single character                           |
+| `[seq]`  | matches any character in `seq`                         |
+| `[!seq]` | matches any character not in `seq`                     |
+
+However, due to the design of `glob.glob`, using a glob pattern such as `config/*`, will **not** match items that being with `.`. To specifically capture items that being with `.`, you will need to include the `.` in the pattern, like this: `config/.*`.
 
 #### Example
 
@@ -209,6 +215,10 @@ like this: `config/.*`.
     ~/.hammerspoon:
       if: '[ `uname` = Darwin ]'
       path: hammerspoon
+    ~/:
+      glob: true
+      path: dotconf/*
+      prefix: '.'
 ```
 
 If the source location is omitted or set to `null`, Dotbot will use the

dotbot/plugins/link.py

@@ -33,6 +33,7 @@ class Link(dotbot.Plugin):
             relink = defaults.get('relink', False)
             create = defaults.get('create', False)
             use_glob = defaults.get('glob', False)
+            base_prefix = defaults.get('prefix', '')
             test = defaults.get('if', None)
             ignore_missing = defaults.get('ignore-missing', False)
             exclude_paths = defaults.get('exclude', [])
@@ -45,6 +46,7 @@ class Link(dotbot.Plugin):
                 relink = source.get('relink', relink)
                 create = source.get('create', create)
                 use_glob = source.get('glob', use_glob)
+                base_prefix = source.get('prefix', base_prefix)
                 ignore_missing = source.get('ignore-missing', ignore_missing)
                 exclude_paths = source.get('exclude', exclude_paths)
                 path = self._default_source(destination, source.get('path'))
@@ -80,6 +82,9 @@ class Link(dotbot.Plugin):
                         # Find common dirname between pattern and the item:
                         glob_dirname = os.path.dirname(os.path.commonprefix([path, glob_full_item]))
                         glob_item = (glob_full_item if len(glob_dirname) == 0 else glob_full_item[len(glob_dirname) + 1:])
+                        # Add prefix to basepath, if provided
+                        if base_prefix:
+                          glob_item = base_prefix + glob_item
                         # where is it going
                         glob_link_destination = os.path.join(destination, glob_item)
                         if create:

test/tests/link-prefix.bash

@@ -0,0 +1,23 @@
+test_description='link prefix'
+. '../test-lib.bash'
+
+test_expect_success 'setup' '
+mkdir ${DOTFILES}/conf &&
+echo "apple" > ${DOTFILES}/conf/a &&
+echo "banana" > ${DOTFILES}/conf/b &&
+echo "cherry" > ${DOTFILES}/conf/c
+'
+
+test_expect_success 'test glob w/ prefix' '
+run_dotbot -v <<EOF
+- link:
+    ~/:
+      glob: true
+      path: conf/*
+      prefix: '.'
+EOF
+
+grep "apple" ~/.a &&
+grep "banana" ~/.b &&
+grep "cherry" ~/.c
+'