Add documentation for .dockerignore

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

docs/buildah-add.md

@@ -47,5 +47,52 @@ buildah add containerID 'https://github.com/containers/buildah/blob/master/READM
 
 buildah add containerID 'passwd' 'certs.d' /etc
 
+## FILES
+
+### `.dockerignore`
+
+If the file .dockerignore exists in the context directory, `buildah copy` reads
+its contents. Buildah uses the content to exclude files and directories from
+the context directory, when copying content into the image.
+
+Users can specify a series of Unix shell globals in a .dockerignore file to
+identify files to exclude.
+
+Buildah supports a special wildcard string `**` which matches any number of
+directories (including zero). For example, **/*.go will exclude all files that
+end with .go that are found in all directories.
+
+Example .dockerignore file:
+
+```
+# comment
+*/temp*
+**/temp*
+temp?
+```
+
+`*/temp*`
+Excludes files and directories whose names start with temp in any immediate subdirectory of the root. For example, the plain file /somedir/temporary.txt is excluded, as is the directory /somedir/temp.
+
+`**/temp*`
+Excludes files and directories starting with temp from any subdirectory.
+
+`temp?`
+Excludes files and directories in the root directory whose names are a one-character extension of temp. For example, /tempa and /tempb are excluded.
+
+Lines starting with ! (exclamation mark) can be used to make exceptions to
+exclusions. The following is an example .dockerignore file that uses this
+mechanism:
+```
+*.md
+!README.md
+```
+
+All markdown files except README.md are excluded from the context.
+
+For more information see:
+
+https://docs.docker.com/engine/reference/builder/#dockerignore-file
+
 ## SEE ALSO
 buildah(1)

docs/buildah-bud.md

@@ -722,6 +722,52 @@ are stored while pulling and pushing images.  Defaults to '/var/tmp'.
 
 ## Files
 
+### `.dockerignore`
+
+If the file .dockerignore exists in the context directory, `buildah bud` reads
+its contents. Buildah uses the content to exclude files and directories from
+the context directory, when executing COPY and ADD directives in the
+Containerfile/Dockerfile
+
+Users can specify a series of Unix shell globals in a .dockerignore file to
+identify files to exclude.
+
+Buildah supports a special wildcard string `**` which matches any number of
+directories (including zero). For example, **/*.go will exclude all files that
+end with .go that are found in all directories.
+
+Example .dockerignore file:
+
+```
+# comment
+*/temp*
+**/temp*
+temp?
+```
+
+`*/temp*`
+Excludes files and directories whose names start with temp in any immediate subdirectory of the root. For example, the plain file /somedir/temporary.txt is excluded, as is the directory /somedir/temp.
+
+`**/temp*`
+Excludes files and directories starting with temp from any subdirectory.
+
+`temp?`
+Excludes files and directories in the root directory whose names are a one-character extension of temp. For example, /tempa and /tempb are excluded.
+
+Lines starting with ! (exclamation mark) can be used to make exceptions to
+exclusions. The following is an example .dockerignore file that uses this
+mechanism:
+```
+*.md
+!README.md
+```
+
+All markdown files except README.md are excluded from the context.
+
+For more information see:
+
+https://docs.docker.com/engine/reference/builder/#dockerignore-file
+
 **registries.conf** (`/etc/containers/registries.conf`)
 
 registries.conf is the configuration file which specifies which container registries should be consulted when completing image names which do not include a registry or domain portion.

docs/buildah-copy.md

@@ -45,5 +45,52 @@ buildah copy containerID 'https://github.com/containers/buildah' '/tmp'
 
 buildah copy containerID 'passwd' 'certs.d' /etc
 
+## FILES
+
+### `.dockerignore`
+
+If the file .dockerignore exists in the context directory, `buildah copy` reads
+its contents. Buildah uses the content to exclude files and directories from
+the context directory, when copying content into the image.
+
+Users can specify a series of Unix shell globals in a .dockerignore file to
+identify files to exclude.
+
+Buildah supports a special wildcard string `**` which matches any number of
+directories (including zero). For example, **/*.go will exclude all files that
+end with .go that are found in all directories.
+
+Example .dockerignore file:
+
+```
+# comment
+*/temp*
+**/temp*
+temp?
+```
+
+`*/temp*`
+Excludes files and directories whose names start with temp in any immediate subdirectory of the root. For example, the plain file /somedir/temporary.txt is excluded, as is the directory /somedir/temp.
+
+`**/temp*`
+Excludes files and directories starting with temp from any subdirectory.
+
+`temp?`
+Excludes files and directories in the root directory whose names are a one-character extension of temp. For example, /tempa and /tempb are excluded.
+
+Lines starting with ! (exclamation mark) can be used to make exceptions to
+exclusions. The following is an example .dockerignore file that uses this
+mechanism:
+```
+*.md
+!README.md
+```
+
+All markdown files except README.md are excluded from the context.
+
+For more information see:
+
+https://docs.docker.com/engine/reference/builder/#dockerignore-file
+
 ## SEE ALSO
 buildah(1)