Added File operators

pkg/yqlib/doc/File Operators.md

@@ -1,13 +1,13 @@
-The file operator is used to filter based on filename. This is most often used with merge when needing to merge specific files together.
+File operators are most often used with merge when needing to merge specific files together. Note that when doing this, you will need to use `eval-all` to ensure all yaml documents are loaded into memory before performing the merge (as opposed to `eval` which runs the expression once per document).
 
 ```bash
-yq eval 'filename == "file1.yaml" * fileIndex == 0' file1.yaml file2.yaml
+yq eval-all 'select(fileIndex == 0) * select(filename == "file2.yaml")' file1.yaml file2.yaml
 ```
 ## Examples
 ### Get filename
 Given a sample.yml file of:
 ```yaml
-'': null
+a: cat
 ```
 then
 ```bash
@@ -21,7 +21,7 @@ sample.yaml
 ### Get file index
 Given a sample.yml file of:
 ```yaml
-'': null
+a: cat
 ```
 then
 ```bash

pkg/yqlib/doc/headers/File Operators.md

@@ -1,5 +1,5 @@
-The file operator is used to filter based on filename. This is most often used with merge when needing to merge specific files together.
+File operators are most often used with merge when needing to merge specific files together. Note that when doing this, you will need to use `eval-all` to ensure all yaml documents are loaded into memory before performing the merge (as opposed to `eval` which runs the expression once per document).
 
 ```bash
-yq eval 'filename == "file1.yaml" * fileIndex == 0' file1.yaml file2.yaml
+yq eval-all 'select(fileIndex == 0) * select(filename == "file2.yaml")' file1.yaml file2.yaml
 ```

pkg/yqlib/lib.go

@@ -18,8 +18,6 @@ type OperationType struct {
 
 // operators TODO:
 // - get path operator (like doc index)
-// - get file index op (like doc index)
-// - get file name op (like doc index)
 // - write in place
 // - mergeAppend (merges and appends arrays)
 // - mergeEmpty (sets only if the document is empty, do I do that now?)

pkg/yqlib/operator_file_test.go

@@ -7,7 +7,7 @@ import (
 var fileOperatorScenarios = []expressionScenario{
 	{
 		description: "Get filename",
-		document:    `{}`,
+		document:    `{a: cat}`,
 		expression:  `filename`,
 		expected: []string{
 			"D0, P[], (!!str)::sample.yml\n",
@@ -15,7 +15,7 @@ var fileOperatorScenarios = []expressionScenario{
 	},
 	{
 		description: "Get file index",
-		document:    `{}`,
+		document:    `{a: cat}`,
 		expression:  `fileIndex`,
 		expected: []string{
 			"D0, P[], (!!int)::0\n",