feat: add ability to specify a custom build directory for an app

docs/deployment/builders/builder-management.md

@@ -47,6 +47,34 @@ The default value may be set by passing an empty value for the option.
 dokku builder:set --global selected
 ```
 
+#### Changing the build directory
+
+> Warning: Please keep in mind that setting a custom build directory will result in loss of any changes to the top-level directory, such as the `git.keep-git-dir` property.
+
+When deploying a monorepo, it may be desirable to specify the specific build directory to use for a given app. This can be done via the `builder:set` command.
+
+```shell
+dokku builder:set node-js-app build-dir app2
+```
+
+The default value may be set by passing an empty value for the option:
+
+```shell
+dokku builder:set node-js-app build-dir
+```
+
+The `build-dir` property can also be set globally. The global default is empty string, and the global value is used when no app-specific value is set.
+
+```shell
+dokku builder:set --global build-dir app2
+```
+
+The default value may be set by passing an empty value for the option.
+
+```shell
+dokku builder:set --global build-dir
+```
+
 ### Displaying builder reports for an app
 
 You can get a report about the app's builder status using the `builder:report` command:
@@ -57,15 +85,24 @@ dokku builder:report
 
 ```
 =====> node-js-app builder information
-       Builder computed selected: herokuish
+       Builder build dir:          custom
+       Builder computed build dir: custom
+       Builder computed selected:  herokuish
+       Builder global build dir:
        Builder global selected: herokuish
        Builder selected: herokuish
 =====> python-sample builder information
+       Builder build dir:
+       Builder computed build dir:
        Builder computed selected: dockerfile
+       Builder global build dir:
        Builder global selected: herokuish
        Builder selected: dockerfile
 =====> ruby-sample builder information
+       Builder build dir:
+       Builder computed build dir:
        Builder computed selected: herokuish
+       Builder global build dir:
        Builder global selected: herokuish
        Builder selected:
 ```

docs/development/plugin-triggers.md

@@ -342,6 +342,31 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 curl "http://httpstat.us/200"
 ```
 
+### `core-post-extract`
+
+> To avoid issues with community plugins, this plugin trigger should be used *only* for core plugins. Please avoid using this trigger in your own plugins.
+
+- Description: Allows you to modify the contents of an app *after* it has been extracted from git/tarball but *before* the image source type is detected.
+- Invoked by: `dokku tar:in`, `dokku tar:from` and the `receive-app` plugin trigger
+- Arguments: `$APP` `$TMP_WORK_DIR` `$REV`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+# Adds a clock process to an app's Procfile
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
+APP="$1"
+TMP_WORK_DIR="$2"
+REV="$3" # optional, may not be sent for tar-based builds
+
+pushd "$TMP_WORK_DIR" >/dev/null
+touch Procfile
+echo "clock: some-command" >> Procfile
+popd &>/dev/null
+```
+
 ### `cron-write`
 
 - Description: Force triggers writing out cron entries

plugins/20_events/core-post-extract

@@ -0,0 +1 @@
+hook

plugins/builder/Makefile

@@ -1,5 +1,5 @@
 SUBCOMMANDS = subcommands/report subcommands/set
-TRIGGERS = triggers/builder-detect triggers/install triggers/post-delete triggers/report
+TRIGGERS = triggers/builder-detect triggers/core-post-extract triggers/install triggers/post-delete triggers/report
 BUILD = commands subcommands triggers
 PLUGIN_NAME = builder
 

plugins/builder/builder.go

@@ -3,11 +3,13 @@ package builder
 var (
 	// DefaultProperties is a map of all valid network properties with corresponding default property values
 	DefaultProperties = map[string]string{
-		"selected": "",
+		"selected":  "",
+		"build-dir": "",
 	}
 
 	// GlobalProperties is a map of all valid global network properties
 	GlobalProperties = map[string]bool{
-		"selected": true,
+		"selected":  true,
+		"build-dir": true,
 	}
 )

plugins/builder/report.go

@@ -11,9 +11,12 @@ func ReportSingleApp(appName string, format string, infoFlag string) error {
 	}
 
 	flags := map[string]common.ReportFunc{
-		"--builder-computed-selected": reportComputedSelected,
+		"--builder-computed-selected":  reportComputedSelected,
-		"--builder-global-selected":   reportGlobalSelected,
+		"--builder-global-selected":    reportGlobalSelected,
-		"--builder-selected":          reportSelected,
+		"--builder-selected":           reportSelected,
+		"--builder-computed-build-dir": reportComputedBuildDir,
+		"--builder-global-build-dir":   reportGlobalBuildDir,
+		"--builder-build-dir":          reportBuildDir,
 	}
 
 	flagKeys := []string{}
@@ -42,3 +45,19 @@ func reportGlobalSelected(appName string) string {
 func reportSelected(appName string) string {
 	return common.PropertyGet("builder", appName, "selected")
 }
+
+func reportComputedBuildDir(appName string) string {
+	value := reportBuildDir(appName)
+	if value == "" {
+		value = reportGlobalBuildDir(appName)
+	}
+
+	return value
+}
+func reportGlobalBuildDir(appName string) string {
+	return common.PropertyGet("builder", "--global", "build-dir")
+}
+
+func reportBuildDir(appName string) string {
+	return common.PropertyGet("builder", appName, "build-dir")
+}

plugins/builder/triggers.go

@@ -2,6 +2,10 @@ package builder
 
 import (
 	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
 
 	"github.com/dokku/dokku/plugins/common"
 )
@@ -21,6 +25,42 @@ func TriggerBuilderDetect(appName string) error {
 	return nil
 }
 
+// TriggerCorePostExtract moves a configured build-dir to be in the app root dir
+func TriggerCorePostExtract(appName string, sourceWorkDir string) error {
+	buildDir := strings.Trim(reportComputedBuildDir(appName), "/")
+	if buildDir == "" {
+		return nil
+	}
+
+	newSourceWorkDir := filepath.Join(sourceWorkDir, buildDir)
+	if !common.DirectoryExists(newSourceWorkDir) {
+		return fmt.Errorf("Specified build-dir not found in sourcecode working directory: %v", buildDir)
+	}
+
+	tmpWorkDir, err := ioutil.TempDir(os.TempDir(), fmt.Sprintf("dokku-%s-%s", common.MustGetEnv("DOKKU_PID"), "CorePostExtract"))
+	if err != nil {
+		return fmt.Errorf("Unable to create temporary working directory: %v", err.Error())
+	}
+
+	if err := os.RemoveAll(tmpWorkDir); err != nil {
+		return fmt.Errorf("Unable to clear out temporary working directory for rewrite: %v", err.Error())
+	}
+
+	if err := os.Rename(newSourceWorkDir, tmpWorkDir); err != nil {
+		return fmt.Errorf("Unable to move build-dir to temporary working directory: %v", err.Error())
+	}
+
+	if err := os.RemoveAll(sourceWorkDir); err != nil {
+		return fmt.Errorf("Unable to clear out sourcecode working directory for rewrite: %v", err.Error())
+	}
+
+	if err := os.Rename(tmpWorkDir, sourceWorkDir); err != nil {
+		return fmt.Errorf("Unable to move build-dir to sourcecode working directory: %v", err.Error())
+	}
+
+	return nil
+}
+
 // TriggerInstall runs the install step for the builder plugin
 func TriggerInstall() error {
 	if err := common.PropertySetup("builder"); err != nil {

plugins/git/functions

@@ -51,6 +51,7 @@ git_trigger_build() {
   declare APP="$1" TMP_WORK_DIR="$2" REV="$3"
   local BUILDER
 
+  plugn trigger core-post-extract "$APP" "$TMP_WORK_DIR" "$REV"
   plugn trigger post-extract "$APP" "$TMP_WORK_DIR" "$REV"
 
   BUILDER="$(plugn trigger builder-detect "$APP" "$TMP_WORK_DIR" | head -n1 || true)"

plugins/tar/functions

@@ -43,6 +43,7 @@ tar_trigger_build() {
   declare APP="$1" TMP_WORK_DIR="$2" REV="$3"
   local BUILDER
 
+  plugn trigger core-post-extract "$APP" "$TMP_WORK_DIR" "$REV"
   plugn trigger post-extract "$APP" "$TMP_WORK_DIR" "$REV"
 
   BUILDER="$(plugn trigger builder-detect "$APP" "$TMP_WORK_DIR" | head -n1 || true)"