doc: regular updates; New update cmd ref

src/Documentation/glossary.js

@@ -14,12 +14,13 @@ export default {
     },
     {
       name: 'DVC cache',
-      match: ['cache'],
+      match: ['DVC cache', 'cache', 'cache directory'],
       desc:
-        'DVC cache is a hidden storage which is by default found at ' +
-        '`.dvc/cache`. This storage is used to manage different versions of ' +
-        'files which are under DVC control. For more information on cache, ' +
-        'please refer to this [guide](/doc/commands-reference/config#cache).'
+        'The DVC cache is a hidden storage (by default located in the ' +
+        '`.dvc/cache` directory) for files that are under DVC control, and ' +
+        'their different versions. For more details, please refer to this ' +
+        '[document](/doc/user-guide/dvc-files-and-directories' +
+        '#structure-of-cache-directory).'
     },
     {
       name: 'Data artifact',
@@ -29,6 +30,13 @@ export default {
         'result (such as extracted features or a ML model file) that is ' +
         'under DVC control. Refer to [Data and Model Files Versioning]' +
         '(/doc/use-cases/data-and-model-files-versioning) for more details.'
+    },
+    {
+      name: 'Import stage',
+      match: ['import stage', 'import stages'],
+      desc:
+        'Stage (DVC-file) created with the `dvc import` or `dvc import-url` ' +
+        'commands. They represent files or directories from external sources.'
     }
   ]
 }

src/Documentation/sidebar.json

@@ -126,6 +126,7 @@
       "status.md",
       "unlock.md",
       "unprotect.md",
+      "update.md",
       "version.md"
     ],
     "labels": {
@@ -170,6 +171,7 @@
       "status.md": "status",
       "unlock.md": "unlock",
       "unprotect.md": "unprotect",
+      "update.md": "update",
       "version.md": "version"
     }
   },

static/docs/commands-reference/checkout.md

@@ -39,6 +39,7 @@ The execution of `dvc checkout` does:
   on the command line. And if the `--with-deps` option is specified, it scans
   backward from the given `targets` in the corresponding
   [pipeline](/doc/get-started/pipeline).
+
 - For any data files where the checksum doesn't match their DVC-file entry, the
   data file is restored from the cache. The link strategy used (`reflink`,
   `hardlink`, `symlink`, or `copy`) depends on the OS and the configured value
@@ -82,7 +83,7 @@ be pulled from a remote cache using `dvc pull`.
   DVC will not checkout files referenced in later stage(s) than `targets`.
 
 - `-R`, `--recursive` - `targets` is expected to contain at least one directory
-  path for this option to have effect. Determines the files to checout by
+  path for this option to have effect. Determines the files to checkout by
   searching each target directory and its subdirectories for DVC-files to
   inspect.
 

static/docs/commands-reference/commit.md

@@ -26,12 +26,14 @@ tying stages or a pipeline.
   code, configuration, or data. Run DVC commands (`dvc run`, `dvc repro`, and
   even `dvc add`) using the `--no-commit` option to avoid caching unnecessary
   data over and over again. Use `dvc commit` when the files are finalized.
+
 - One can always execute the code used in a stage without using DVC (keep in
   mind that output files or directories in certain cases must first be
   unprotected or removed, see `dvc unprotect`). Or one could be developing code
   or data, repeatedly manually executing the code until it is working. Once it
   is finished, use `dvc add`, `dvc commit`, or `dvc run` when appropriate to
   update DVC-files and to store data to the cache.
+
 - Sometimes we want to clean up a code or configuration file in a way that
   doesn't cause a change in its results. We might write in-line documentation
   with comments, change indentation, remove some debugging printouts, or any
@@ -47,12 +49,12 @@ want. Let's take a look at what is happening in the fist scenario closely:
 Normally DVC commands like `dvc add`, `dvc repro` or `dvc run`, commit the data
 to the DVC cache as the last step. What _commit_ means is that DVC:
 
-- Computes a checksum for the file/directory.
-- Enters the checksum and file name into the DVC-file.
-- Tells the SCM to ignore the file/directory (e.g. add entry to `.gitignore`).
-  Note that if the workspace was initialized with no SCM support
-  (`dvc init --no-scm`), this does not happen.
-- Adds the file/directory or to the DVC cache.
+- Computes a checksum for the file/directory
+- Enters the checksum and file name into the DVC-file
+- Tells the SCM to ignore the file/directory (e.g. add entry to `.gitignore`)
+  (Note that if the workspace was initialized with no SCM support
+  (`dvc init --no-scm`), this does not happen.)
+- Adds the file/directory or to the DVC cache
 
 There are many cases where the last step is not desirable (usually, rapid
 iteration on some experiment). For the DVC commands where available, the
@@ -211,7 +213,7 @@ execute this set of commands:
 ```dvc
 $ dvc commit
 $ dvc status
-Pipeline is up to date. Nothing to reproduce.
+Pipelines are up to date. Nothing to reproduce.
 $ ls .dvc/cache/70
 599f166c2098d7ffca91a369a78b0d
 ```
@@ -252,8 +254,8 @@ train.dvc:
         modified:           src/train.py
 ```
 
-Let's edit one of the source files. It doesn't matter which one. You'll see that
-both Git and DVC recognize a change was made.
+Let's edit one of the source code files. It doesn't matter which one. You'll see
+that both Git and DVC recognize a change was made.
 
 If we ran `dvc repro` at this point, this pipeline would be reproduced. But
 since the change was inconsequential, that would be a waste of time and CPU.
@@ -273,7 +275,7 @@ Are you sure you commit it? [y/n] y
 
 $ dvc status
 
-Pipeline is up to date. Nothing to reproduce.
+Pipelines are up to date. Nothing to reproduce.
 ```
 
 Nothing special is required, we simply `commit` to both the SCM and DVC. Since

static/docs/commands-reference/diff.md

@@ -27,6 +27,11 @@ were deleted/changed, and the file size differences.
 Note that `dvc diff` does not show the line-to-line comparison among the target
 files in each revision, like `git diff` does.
 
+> For an example on how to create line-to-line text file comparison refer to
+> issue
+> [#770](https://github.com/iterative/dvc/issues/770#issuecomment-512693256) in
+> our code repository.
+
 If the `-t` option is used, the diff is limited to the `TARGET` file or
 directory specified.
 
@@ -35,9 +40,9 @@ by the Git SCM, for example when `dvc init` was used with the `--no-scm` option.
 
 ## Options
 
-- `-t TARGET`, `--target TARGET` - Source path to a data file or directory. If
-  not specified, compares all files and directories that are under DVC control
-  in the workspace.
+- `-t TARGET`, `--target TARGET` - path to a data file or directory. If not
+  specified, compares all files and directories that are under DVC control in
+  the workspace.
 
 - `-h`, `--help` - prints the usage/help message, and exit.
 

static/docs/commands-reference/fetch.md

@@ -309,4 +309,4 @@ the workspace (with `dvc repro train.dvc`).
 > Note that in this sample project, the last stage file `evaluate.dvc` doesn't
 > add any more data files than those form previous stages so at this point all
 > of the files for this pipeline are in local cache and `dvc status -c` would
-> output "Pipeline is up to date. Nothing to reproduce."
+> output `Pipelines are up to date.`

static/docs/commands-reference/get.md

@@ -33,7 +33,7 @@ single-purpose command that can be used out of the box after installing DVC.
 > See `dvc get-url` to download data from other supported URLs.
 
 After running this command successfully, the data found in the `url` `path` is
-created in the current working directory with its original file name.
+created in the current working directory, with its original file name.
 
 ## Options
 
@@ -44,4 +44,41 @@ created in the current working directory with its original file name.
 
 - `-v`, `--verbose` - displays detailed tracing information.
 
-<!--  ## Example -->
+## Example:
+
+> Note that `dvc get` can be used form anywhere in the file system, as long as
+> DVC is [installed](/doc/get-started/install).
+
+We can use `dvc get` to download the resulting model file from our
+[get started example](https://github.com/iterative/example-get-started), which
+is a DVC project external to the current working directory). The desired file is
+located in the root of the external repo, and named `model.pkl`.
+
+```dvc
+$ dvc get https://github.com/iterative/example-get-started model.pkl
+Preparing to download data from 'https://remote.dvc.org/get-started'
+...
+$ ls
+model.pkl
+```
+
+Note that the `model.pkl` file doesn't actually exist in the
+[data directory](https://github.com/iterative/example-get-started/tree/master/)
+of the external Git repo. Instead, the corresponding DVC-file
+[train.dvc](https://github.com/iterative/example-get-started/blob/master/train.dvc)
+is found, which specifies `model.pkl` in its outputs (`outs`). DVC then
+[pulls](/doc/commands-reference/pull) the file from the default
+[remote](/doc/commands-reference/remote) of the external DVC project (found in
+its
+[config file](https://github.com/iterative/example-get-started/blob/master/.dvc/config)).
+
+A common use for downloading binary files from DVC repos, as done in this
+example, is to place a ML model inside a wrapper application that serves as an
+[ETL](https://en.wikipedia.org/wiki/Extract,_transform,_load) pipeline or as an
+HTTP/RESTful API (web service) that provides predictions upon request. This can
+be automated leveraging DVC with [CI/CD](https://en.wikipedia.org/wiki/CI/CD)
+tools.
+
+The same example applies to raw or intermediate data files as well, of course,
+for cases where we want to download those files and perform some analysis on
+them.

static/docs/commands-reference/import-url.md

@@ -2,7 +2,7 @@
 
 Download or copy file or directory from any supported URL (for example `s3://`,
 `ssh://`, and other protocols) or local directory to the <abbr>workspace</abbr>,
-and track changes in the remote source with DVC. Creates a DVC-file.
+and track changes in the remote data source with DVC. Creates a DVC-file.
 
 > See also `dvc get-url` which corresponds to the first step this command
 > performs (just download the data).
@@ -20,13 +20,13 @@ positional arguments:
 ## Description
 
 In some cases it's convenient to add a data file or directory from a remote
-location into the workspace, such that it will be automatically updated when the
-external data source changes. Examples:
+location into the workspace, such that it will be automatically updated (by
+`dvc repro`) when the external data source changes. Examples:
 
-- A remote system may produce occasional data files that are used in other
-  projects.
-- A batch process running regularly updates a data file to import.
-- A shared dataset on a remote storage that is managed and updated outside DVC.
+- a remote system may produce occasional data files that are used in other
+  projects;
+- a batch process running regularly updates a data file to import; and
+- a shared dataset on a remote storage that is managed and updated outside DVC.
 
 The `dvc import-url` command helps the user create such an external data
 dependency. The `url` argument specifies the external location of the data to be
@@ -95,11 +95,12 @@ dependency. The `dvc import-url` command saves the user from having to manually
 copy files from each of the remote storage schemes, and from having to install
 CLI tools for each service.
 
-When DVC inspects a DVC-file, its dependencies will be checked to see if any
-have changed. A changed dependency will appear in the `dvc status` report,
-indicating the need to reproduce this import stage. When DVC inspects an
-external dependency, it uses a method appropriate to that dependency to test its
-current status.
+Note that by default, import stages are locked in their DVC-files (with
+`locked: true`). Use `dvc update` manually on them to force updating the
+downloaded file or directory from the external data source.
+
+> If `dvc unlock` is used on locked stages, they will start to be checked by
+> `dvc status`, and updated by `dvc repro`.
 
 ## Options
 
@@ -164,8 +165,8 @@ using `dvc import-url`:
 
 ### Click and expand to prepare the workspace
 
-This is needed to actually run the command below in case you are reproducing
-this example:
+This is needed to actually run the command below in case you are trying this
+example:
 
 ```dvc
 $ git checkout 2-remote
@@ -223,8 +224,8 @@ file has changed.
 
 What if that remote file is one which will be updated regularly? The project
 goal might include regenerating a <abbr>data artifact</abbr> based on the
-updated source. A pipeline can be triggered to re-execute based on a changed
-external dependency.
+updated data source. A pipeline can be triggered to re-execute based on a
+changed external dependency.
 
 Let us again use the [Getting Started](/doc/get-started) example, in a way which
 will mimic an updated external data source.
@@ -348,7 +349,7 @@ $ tree
 3 directories, 10 files
 
 $ dvc status
-Pipeline is up to date. Nothing to reproduce.
+Pipelines are up to date. Nothing to reproduce.
 ```
 
 Then in the data store directory, edit `data.xml`. It doesn't matter what you
@@ -362,8 +363,8 @@ data.xml.dvc:
         modified:     /path/to/data-store/data.xml
 ```
 
-DVC has noticed the external dependency has changed. It is telling us that it is
-necessary to now run `dvc repro`.
+DVC has noticed the external dependency (import stage) has changed. It is
+telling us that it is necessary to now run `dvc repro`.
 
 ```dvc
 $ dvc repro prepare.dvc
@@ -396,11 +397,11 @@ $ git commit -a -m "updated data"
  2 files changed, 6 insertions(+), 6 deletions(-)
 
 $ dvc status
-Pipeline is up to date. Nothing to reproduce.
+Pipelines are up to date. Nothing to reproduce.
 ```
 
-Because the external source for the data file changed, the change was noticed by
-the `dvc status` command. Running `dvc repro` then ran both stages of this
-pipeline, and if we had set up the other stages they also would have been run.
-It first downloaded the updated data file. And then noticing that
+Because the external data source for the data file changed, the change was
+noticed by the `dvc status` command. Running `dvc repro` then ran both stages of
+this pipeline, and if we had set up the other stages they also would have been
+run. It first downloaded the updated data file. And then noticing that
 `data/data.xml` had changed, that triggered the `prepare.dvc` stage to execute.

static/docs/commands-reference/import.md

@@ -5,7 +5,7 @@
 
 Download or copy file or directory from another DVC repository (on a git server
 such as Github) into the <abbr>workspace</abbr>, and track changes in the remote
-source with DVC. Creates a DVC-file.
+data source with DVC. Creates a DVC-file.
 
 > See also `dvc get` which corresponds to the first step this command performs
 > (just download the data).
@@ -25,8 +25,8 @@ positional arguments:
 DVC provides an easy way to reuse datasets, intermediate results, ML models, or
 other files and directories tracked in another DVC repository into the present
 <abbr>workspace</abbr>. The `dvc import` command downloads such a <abbr>data
-artifact</abbr> in a way that it can be tracked with DVC, resulting in automatic
-updates when the external data source changes.
+artifact</abbr> in a way that it is tracked with DVC, so it can be updated when
+the external data source changes.
 
 The `url` argument specifies the external DVC project's Git repository URL (both
 HTTP and SSH protocols supported, e.g. `[user@]server:project.git`), while
@@ -50,6 +50,13 @@ determine whether the local copy is out of date.
 To actually [track the data](https://dvc.org/doc/get-started/add-files),
 `git add` (and `git commit`) the import stage (DVC-file).
 
+Note that by default, these import stages are locked in their DVC-files (with
+fields `locked: true` and `rev_lock`). Use `dvc update` manually on them to
+force updating the downloaded data artifact from the external DVC repo.
+
+> If `dvc unlock` is used on locked stages, they will start to be checked by
+> `dvc status`, and updated by `dvc repro`.
+
 ## Options
 
 - `-o`, `--out` - specify a location in the workspace to place the imported data
@@ -65,5 +72,3 @@ To actually [track the data](https://dvc.org/doc/get-started/add-files),
   problems arise, otherwise 1.
 
 - `-v`, `--verbose` - displays detailed tracing information.
-
-<!-- ## Example -->

static/docs/commands-reference/index.md

@@ -2,16 +2,16 @@
 
 DVC is a command-line tool. The typical use case for DVC goes as follows
 
-- In an existing Git repository, initialize a DVC repository with `dvc init`.
-- Copy source files for modeling into the repository and convert the files into
-  DVC data files with `dvc add` command.
-- Process source data files through your data processing and modeling code using
-  the `dvc run` command.
+- In an existing Git repository, initialize a DVC repository with `dvc init`,
+- Copy source code files for modeling into the repository and convert the files
+  into DVC data files with `dvc add` command;
+- Process raw data files through your data processing and modeling code using
+  the `dvc run` command;
 - Use `--outs` option to specify `dvc run` command outputs which will be
-  converted to DVC data files after the code runs.
+  converted to DVC data files after the code runs;
 - Clone a git repo with the code of your ML application pipeline. However, this
   will not copy your DVC cache. Use
   [data remotes](/doc/commands-reference/remote) and `dvc push` to share the
-  cache (data).
+  cache (data);
 - Use `dvc repro` to quickly reproduce your pipeline on a new iteration, after
   your data item files or source code of your ML application are modified.