compose: implement configurable subject prefix stripping when replying

Introduce functionality to strip email subject from a set list of
prefixes or from a user set list.

Also, added a setting for the reply prefix (default is "Re:").

Closes #142

docs/meli.conf.5

@@ -540,6 +540,24 @@ Whether the strftime call for the attribution string uses the POSIX locale inste
 Forward emails as attachment? (Alternative is inline).
 .\" default value
 .Pq Em ask
+.It Ic reply_prefix_list_to_strip Ar [String]
+.Pq Em optional
+Alternative lists of reply prefixes (etc. ["Re:", "RE:", ...]) to strip.
+.\" default value
+.Pq Em ["Re:", "RE:", "Fwd:", "Fw:", "回复:", "回覆:", "SV:", "Sv:", "VS:", "Antw:", "Doorst:", "VS:", "VL:", "REF:", "TR:", "TR:", "AW:", "WG:", "ΑΠ:", "Απ:", "απ:", "ΠΡΘ:", "Πρθ:", "πρθ:", "ΣΧΕΤ:", "Σχετ:", "σχετ:", "ΠΡΘ:", "Πρθ:", "πρθ:", "Vá:", "Továbbítás:", "R:", "I:", "RIF:", "FS:", "BLS:", "TRS:", "VS:", "VB:", "RV:", "RES:", "Res", "ENC:", "Odp:", "PD:", "YNT:", "İLT:", "ATB:", "YML:"]
+.It Ic reply_prefix Ar String
+.Pq Em optional
+The prefix to use in reply subjects.
+The de facto prefix is "Re:".
+.\" default value
+.Pq Em `Re:`
+.Pp
+RFC 2822, "Internet Message Format" has this to say on the matter:
+.Bd -literal -offset indent -compact
+When used in a reply, the field body MAY start with the string "Re: " (from
+the Latin "res", in the matter of) followed by the contents of the "Subject:"
+field body of the original message.
+.Ed
 .El
 .Sh SHORTCUTS
 Shortcuts can take the following values:

src/components/mail/compose.rs

@@ -219,15 +219,34 @@ impl Composer {
         let mut ret = Composer::with_account(coordinates.0, context);
         let account = &context.accounts[&coordinates.0];
         let envelope = account.collection.get_env(coordinates.2);
+        let subject = {
             let subject = envelope.subject();
-        ret.draft.set_header(
-            "Subject",
-            if !subject.starts_with("Re: ") {
-                format!("Re: {}", subject)
+            let prefix_list = account_settings!(
+                context[ret.account_hash]
+                    .composing
+                    .reply_prefix_list_to_strip
+            )
+            .as_ref()
+            .map(|v| v.iter().map(String::as_str).collect::<Vec<&str>>())
+            .unwrap_or(vec![]);
+            let subject = subject
+                .as_ref()
+                .strip_prefixes_from_list(if prefix_list.is_empty() {
+                    <&str>::USUAL_PREFIXES
                 } else {
-                subject.into()
-            },
-        );
+                    &prefix_list
+                })
+                .to_string();
+
+            let prefix =
+                account_settings!(context[ret.account_hash].composing.reply_prefix).as_str();
+            if !subject.starts_with(prefix) {
+                format!("{prefix} {subject}", prefix = prefix, subject = subject)
+            } else {
+                subject.to_string()
+            }
+        };
+        ret.draft.set_header("Subject", subject);
         ret.draft.set_header(
             "References",
             format!(

src/conf/composing.rs

@@ -77,6 +77,13 @@ pub struct ComposingSettings {
     /// Default: ask
     #[serde(default = "ask", alias = "forward-as-attachment")]
     pub forward_as_attachment: ToggleFlag,
+    /// Alternative lists of reply prefixes (etc. ["Re:", "RE:", ...]) to strip
+    /// Default: `["Re:", "RE:", "Fwd:", "Fw:", "回复:", "回覆:", "SV:", "Sv:", "VS:", "Antw:", "Doorst:", "VS:", "VL:", "REF:", "TR:", "TR:", "AW:", "WG:", "ΑΠ:", "Απ:", "απ:", "ΠΡΘ:", "Πρθ:", "πρθ:", "ΣΧΕΤ:", "Σχετ:", "σχετ:", "ΠΡΘ:", "Πρθ:", "πρθ:", "Vá:", "Továbbítás:", "R:", "I:", "RIF:", "FS:", "BLS:", "TRS:", "VS:", "VB:", "RV:", "RES:", "Res", "ENC:", "Odp:", "PD:", "YNT:", "İLT:", "ATB:", "YML:"]`
+    #[serde(default, alias = "reply-prefix-list-to-strip")]
+    pub reply_prefix_list_to_strip: Option<Vec<String>>,
+    /// The prefix to use in reply subjects. The de facto prefix is "Re:".
+    #[serde(default = "res", alias = "reply-prefix")]
+    pub reply_prefix: String,
 }
 
 impl Default for ComposingSettings {
@@ -92,10 +99,16 @@ impl Default for ComposingSettings {
             attribution_format_string: None,
             attribution_use_posix_locale: true,
             forward_as_attachment: ToggleFlag::Ask,
+            reply_prefix_list_to_strip: None,
+            reply_prefix: res(),
         }
     }
 }
 
+fn res() -> String {
+    "Re:".to_string()
+}
+
 macro_rules! named_unit_variant {
     ($variant:ident) => {
         pub mod $variant {

src/conf/overrides.rs

@@ -323,6 +323,15 @@ pub struct ComposingSettingsOverride {
     #[serde(alias = "forward-as-attachment")]
     #[serde(default)]
     pub forward_as_attachment: Option<ToggleFlag>,
+    #[doc = " Alternative lists of reply prefixes (etc. [\"Re:\", \"RE:\", ...]) to strip"]
+    #[doc = " Default: `[\"Re:\", \"RE:\", \"Fwd:\", \"Fw:\", \"回复:\", \"回覆:\", \"SV:\", \"Sv:\", \"VS:\", \"Antw:\", \"Doorst:\", \"VS:\", \"VL:\", \"REF:\", \"TR:\", \"TR:\", \"AW:\", \"WG:\", \"ΑΠ:\", \"Απ:\", \"απ:\", \"ΠΡΘ:\", \"Πρθ:\", \"πρθ:\", \"ΣΧΕΤ:\", \"Σχετ:\", \"σχετ:\", \"ΠΡΘ:\", \"Πρθ:\", \"πρθ:\", \"Vá:\", \"Továbbítás:\", \"R:\", \"I:\", \"RIF:\", \"FS:\", \"BLS:\", \"TRS:\", \"VS:\", \"VB:\", \"RV:\", \"RES:\", \"Res\", \"ENC:\", \"Odp:\", \"PD:\", \"YNT:\", \"İLT:\", \"ATB:\", \"YML:\"]`"]
+    #[serde(alias = "reply-prefix-list-to-strip")]
+    #[serde(default)]
+    pub reply_prefix_list_to_strip: Option<Option<Vec<String>>>,
+    #[doc = " The prefix to use in reply subjects. The de facto prefix is \"Re:\"."]
+    #[serde(alias = "reply-prefix")]
+    #[serde(default)]
+    pub reply_prefix: Option<String>,
 }
 impl Default for ComposingSettingsOverride {
     fn default() -> Self {
@@ -337,6 +346,8 @@ impl Default for ComposingSettingsOverride {
             attribution_format_string: None,
             attribution_use_posix_locale: None,
             forward_as_attachment: None,
+            reply_prefix_list_to_strip: None,
+            reply_prefix: None,
         }
     }
 }