Add a consolidated file cache

This commits reworks how file caching is performed in Hugo. Now there is only one way, and it can be configured.

This is the default configuration:

```toml
[caches]
[caches.getjson]
dir = ":cacheDir"
maxAge = -1
[caches.getcsv]
dir = ":cacheDir"
maxAge = -1
[caches.images]
dir = ":resourceDir/_gen"
maxAge = -1
[caches.assets]
dir = ":resourceDir/_gen"
maxAge = -1
```

You can override any of these cache setting in your own `config.toml`.

The placeholders explained:

`:cacheDir`: This is the value of the `cacheDir` config option if set (can also be set via OS env variable `HUGO_CACHEDIR`). It will fall back to `/opt/build/cache/hugo_cache/` on Netlify, or a `hugo_cache` directory below the OS temp dir for the others.
`:resourceDir`: This is the value of the `resourceDir` config option.

`maxAge` is the time in seconds before a cache entry will be evicted, -1 means forever and 0 effectively turns that particular cache off.

This means that if you run your builds on Netlify, all caches configured with `:cacheDir` will be saved and restored on the next build. For other CI vendors, please read their documentation. For an CircleCI example, see https://github.com/bep/hugo-sass-test/blob/6c3960a8f4b90e8938228688bc49bdcdd6b2d99e/.circleci/config.yml

Fixes #5404

1 files changed, 4 insertions, 13 deletions

diff --git a/commands/commandeer.go b/commands/commandeer.go
index 545191cfe..cd2866a27 100644
--- a/commands/commandeer.go
+++ b/commands/commandeer.go
@@ -359,20 +359,11 @@ func (c *commandeer) loadConfig(mustHaveConfigFile, running bool) error {
 		return err
 	}
 
-	cacheDir := config.GetString("cacheDir")
-	if cacheDir != "" {
-		if helpers.FilePathSeparator != cacheDir[len(cacheDir)-1:] {
-			cacheDir = cacheDir + helpers.FilePathSeparator
-		}
-		isDir, err := helpers.DirExists(cacheDir, sourceFs)
-		checkErr(cfg.Logger, err)
-		if !isDir {
-			mkdir(cacheDir)
-		}
-		config.Set("cacheDir", cacheDir)
-	} else {
-		config.Set("cacheDir", helpers.GetTempDir("hugo_cache", sourceFs))
+	cacheDir, err := helpers.GetCacheDir(sourceFs, config)
+	if err != nil {
+		return err
 	}
+	config.Set("cacheDir", cacheDir)
 
 	cfg.Logger.INFO.Println("Using config file:", config.ConfigFileUsed())